diff --git a/networkcommons/data/__init__.py b/networkcommons/data/__init__.py
index 1153ac8..2251f98 100644
--- a/networkcommons/data/__init__.py
+++ b/networkcommons/data/__init__.py
@@ -14,5 +14,5 @@
 #
 
 from ._builtin import _module_data, urls
-from .omics import *
-from .network import *
+from . import omics
+from . import network
diff --git a/networkcommons/data/network/lianaplus.py b/networkcommons/data/network/_liana.py
similarity index 86%
rename from networkcommons/data/network/lianaplus.py
rename to networkcommons/data/network/_liana.py
index 16a6c9c..73c9499 100644
--- a/networkcommons/data/network/lianaplus.py
+++ b/networkcommons/data/network/_liana.py
@@ -13,6 +13,16 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+Prior knowledge network used by LIANA+.
+"""
+
+__all__ = ['get_lianaplus']
+
+import lazy_import
+
+liana = lazy_import.lazy_module('liana')
+
 
 def get_lianaplus(resource='Consensus'):
     """
@@ -27,8 +37,6 @@ def get_lianaplus(resource='Consensus'):
         pandas.DataFrame: Liana+ network with source, target, and sign columns.
     """
 
-    import liana
-
     network = liana.resource.select_resource(resource).drop_duplicates()
     network.columns = ['source', 'target']
     network['sign'] = 1
diff --git a/networkcommons/data/network/moon.py b/networkcommons/data/network/_moon.py
similarity index 86%
rename from networkcommons/data/network/moon.py
rename to networkcommons/data/network/_moon.py
index c99ced2..9b49a6f 100644
--- a/networkcommons/data/network/moon.py
+++ b/networkcommons/data/network/_moon.py
@@ -13,26 +13,34 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+Prior knowledge network used by MOON.
+"""
+
+__all__ = ['build_moon_regulons']
+
+import lazy_import
 import numpy as np
 import pandas as pd
 
+dc = lazy_import.lazy_module('decoupler')
+
 from networkcommons import _utils
+from . import _omnipath
+from . import _liana
 
 
 def build_moon_regulons(include_liana=False):
 
-    import decoupler as dc
-    from . import omnipath
-
     dorothea_df = dc.get_collectri()
 
     TFs = np.unique(dorothea_df['source'])
 
-    full_pkn = omnipath.get_omnipath(genesymbols=True, directed_signed=True)
+    full_pkn = _omnipath.get_omnipath(genesymbols=True, directed_signed=True)
 
     if include_liana:
-        from . import lianaplus
-        ligrec_resource = lianaplus.get_lianaplus()
+
+        ligrec_resource = _liana.get_lianaplus()
 
         full_pkn = pd.concat([full_pkn, ligrec_resource])
         full_pkn['edgeID'] = full_pkn['source'] + '_' + full_pkn['target']
diff --git a/networkcommons/data/network/omnipath.py b/networkcommons/data/network/_omnipath.py
similarity index 88%
rename from networkcommons/data/network/omnipath.py
rename to networkcommons/data/network/_omnipath.py
index 10ad2a3..279dbcc 100644
--- a/networkcommons/data/network/omnipath.py
+++ b/networkcommons/data/network/_omnipath.py
@@ -13,12 +13,19 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
-import omnipath as op
+"""
+Access to the OmniPath database.
+"""
+
+__all__ = ['get_omnipath']
+
+import lazy_import
 import numpy as np
 
+op = lazy_import.lazy_module('omnipath')
+
 
-def get_omnipath(genesymbols=True,
-                 directed_signed=True):
+def get_omnipath(genesymbols: bool = True, directed_signed: bool = True):
     """
     Retrieves the Omnipath network with directed interactions
     and specific criteria.
diff --git a/networkcommons/data/omics/__init__.py b/networkcommons/data/omics/__init__.py
index 2ff6c6a..b180689 100644
--- a/networkcommons/data/omics/__init__.py
+++ b/networkcommons/data/omics/__init__.py
@@ -13,8 +13,12 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
-from .decryptm import *
-from .decryptm_ebi import get_decryptm as _get_decryptm
-from .deseq2 import *
-from .panacea import *
-from .scperturb import *
+"""
+Access to public omics datasets.
+"""
+
+from ._common import *
+from ._decryptm import *
+from ._deseq2 import *
+from ._panacea import *
+from ._scperturb import *
diff --git a/networkcommons/data/omics/common.py b/networkcommons/data/omics/_common.py
similarity index 98%
rename from networkcommons/data/omics/common.py
rename to networkcommons/data/omics/_common.py
index f0f57ec..44c7469 100644
--- a/networkcommons/data/omics/common.py
+++ b/networkcommons/data/omics/_common.py
@@ -13,27 +13,28 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+General procedures for downloading omics datasets.
+"""
+
 from __future__ import annotations
 
-from typing import Any, IO
+__all__ = ['datasets']
+
+from typing import IO
 import zipfile
 import os
-import re
-import glob
 import hashlib
 import contextlib
 import urllib.parse
 
-import shutil
 import requests
 import bs4
 import pandas as pd
 
-from .._builtin import _module_data
 from networkcommons import _conf
 from networkcommons._session import _log
-
-__all__ = ['datasets']
+from .._builtin import _module_data
 
 
 def _datasets() -> dict[str, dict]:
diff --git a/networkcommons/data/omics/decryptm.py b/networkcommons/data/omics/_decryptm.py
similarity index 86%
rename from networkcommons/data/omics/decryptm.py
rename to networkcommons/data/omics/_decryptm.py
index 64ea11f..fa210dd 100644
--- a/networkcommons/data/omics/decryptm.py
+++ b/networkcommons/data/omics/_decryptm.py
@@ -13,18 +13,22 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+DecryptM proteomics and phosphoproteomics data.
+"""
+
 from __future__ import annotations
 
+__all__ = ['decryptm_datasets', 'decryptm_table', 'decryptm_experiment']
+
 import os
 import urllib.parse
 
 import pandas as pd
 
-from . import common
+from . import _common
 from networkcommons import _conf
 
-__all__ = ['decryptm_datasets', 'decryptm_table', 'decryptm_experiment']
-
 
 def decryptm_datasets(update: bool = False) -> pd.DataFrame:
     """
@@ -43,7 +47,7 @@ def decryptm_datasets(update: bool = False) -> pd.DataFrame:
 
     if update or not os.path.exists(path):
 
-        baseurl = urllib.parse.urljoin(common._baseurl(), 'decryptm')
+        baseurl = urllib.parse.urljoin(_common._baseurl(), 'decryptm')
 
         datasets = pd.DataFrame(
             [
@@ -52,9 +56,9 @@ def decryptm_datasets(update: bool = False) -> pd.DataFrame:
                     data_type,
                     fname,
                 )
-                for experiment in common._ls(baseurl)
-                for data_type in common._ls(f'{baseurl}/{experiment}')
-                for fname in common._ls(f'{baseurl}/{experiment}/{data_type}')
+                for experiment in _common._ls(baseurl)
+                for data_type in _common._ls(f'{baseurl}/{experiment}')
+                for fname in _common._ls(f'{baseurl}/{experiment}/{data_type}')
                 if fname.startswith('curve')
             ],
             columns = ['experiment', 'data_type', 'fname']
@@ -86,8 +90,8 @@ def decryptm_table(experiment: str, data_type: str, fname: str) -> pd.DataFrame:
         The table as a pandas data frame.
     """
 
-    return common._open(
-        common._commons_url('decryptm', **locals()),
+    return _common._open(
+        _common._commons_url('decryptm', **locals()),
         df = {'sep': '\t'},
     )
 
diff --git a/networkcommons/data/omics/decryptm_ebi.py b/networkcommons/data/omics/_decryptm_ebi.py
similarity index 84%
rename from networkcommons/data/omics/decryptm_ebi.py
rename to networkcommons/data/omics/_decryptm_ebi.py
index ed81290..6f2c2e8 100644
--- a/networkcommons/data/omics/decryptm_ebi.py
+++ b/networkcommons/data/omics/_decryptm_ebi.py
@@ -15,16 +15,18 @@
 
 from __future__ import annotations
 
+__all__ = []
+
 import os
 import shutil
 import glob
 import urllib.parse
 
-from . import common
+from . import _common
 from networkcommons._session import _log
 
 
-def get_decryptm(path: str):
+def _get_decryptm(path: str):
     """
     Download DecryptM from EBI.
 
@@ -35,13 +37,13 @@ def get_decryptm(path: str):
 
     os.makedirs(path, exist_ok = True)
     url = 'https://ftp.pride.ebi.ac.uk/pride/data/archive/2023/03/PXD037285/'
-    files = [f for f in common._ls(url) if f.endswith('Curves.zip')]
+    files = [f for f in _common._ls(url) if f.endswith('Curves.zip')]
 
     for fname in files:
 
         zip_url = urllib.parse.urljoin(url, fname)
 
-        with common._open(zip_url) as zip_file:
+        with _common._open(zip_url) as zip_file:
 
             _log(f'Extracting zip `{zip_file.filename}` to `{path}`.')
             zip_file.extractall(path)
diff --git a/networkcommons/data/omics/deseq2.py b/networkcommons/data/omics/_deseq2.py
similarity index 89%
rename from networkcommons/data/omics/deseq2.py
rename to networkcommons/data/omics/_deseq2.py
index bdb2d8d..c2aa1d4 100644
--- a/networkcommons/data/omics/deseq2.py
+++ b/networkcommons/data/omics/_deseq2.py
@@ -13,8 +13,14 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+Differential expression analysis with DESeq2.
+"""
+
 from __future__ import annotations
 
+__all__ = ['deseq2']
+
 from typing import TYPE_CHECKING
 import multiprocessing
 import importlib
@@ -23,17 +29,16 @@
 
     import pandas as pd
 
+import lazy_import
 from pypath_common import _misc as _ppcommon
-import pydeseq2 as _deseq2
 
 for _mod in ('default_inference', 'dds', 'ds'):
-    importlib.import_module(f'pydeseq2.{_mod}')
+
+    globals()[f'_deseq2_{_mod}'] = lazy_import.lazy_module(f'pydeseq2.{_mod}')
 
 from networkcommons import _conf
 from networkcommons._session import _log
 
-__all__ = ['deseq2']
-
 
 def deseq2(
         counts: pd.DataFrame,
@@ -70,9 +75,9 @@ def deseq2(
     ref_group = ref_group.replace('_', '-')
 
     n_cpus = _conf.get('cpu_count', multiprocessing.cpu_count())
-    inference = _deseq2.default_inference.DefaultInference(n_cpus = n_cpus)
+    inference = _deseq2_default_inference.DefaultInference(n_cpus = n_cpus)
 
-    dds = _deseq2.dds.DeseqDataSet(
+    dds = _deseq2_dds.DeseqDataSet(
         counts=counts.T,
         metadata=metadata,
         design_factors=design_factors,
@@ -82,7 +87,7 @@ def deseq2(
 
     dds.deseq2()
 
-    results = _deseq2.ds.DeseqStats(
+    results = _deseq2_ds.DeseqStats(
         dds,
         contrast=['group', test_group, ref_group],
         inference=inference
diff --git a/networkcommons/data/omics/_moon.py b/networkcommons/data/omics/_moon.py
index 733d043..e985525 100644
--- a/networkcommons/data/omics/_moon.py
+++ b/networkcommons/data/omics/_moon.py
@@ -19,11 +19,11 @@
 
 from __future__ import annotations
 
-import pandas as pd
+__all__ = ['moon']
 
-from . import common
+import pandas as pd
 
-__all__ = ['moon']
+from . import _common
 
 
 def moon() -> dict[str, pd.DataFrame]:
diff --git a/networkcommons/data/omics/panacea.py b/networkcommons/data/omics/_panacea.py
similarity index 77%
rename from networkcommons/data/omics/panacea.py
rename to networkcommons/data/omics/_panacea.py
index d07cc2d..10b1e1c 100644
--- a/networkcommons/data/omics/panacea.py
+++ b/networkcommons/data/omics/_panacea.py
@@ -13,13 +13,18 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+RNA-Seq data from the 'Pancancer Analysis of Chemical Entity Activity'
+resource.
+"""
+
 from __future__ import annotations
 
-import pandas as pd
+__all__ = ['panacea']
 
-from . import common
+import pandas as pd
 
-__all__ = ['panacea']
+from . import _common
 
 
 def panacea() -> tuple[pd.DataFrame]:
@@ -31,8 +36,8 @@ def panacea() -> tuple[pd.DataFrame]:
     """
 
     return tuple(
-        common._open(
-            common._commons_url('panacea', table = table),
+        _common._open(
+            _common._commons_url('panacea', table = table),
             df = {'sep': '\t'},
         )
         for table in ('count', 'meta')
diff --git a/networkcommons/data/omics/scperturb.py b/networkcommons/data/omics/_scperturb.py
similarity index 87%
rename from networkcommons/data/omics/scperturb.py
rename to networkcommons/data/omics/_scperturb.py
index 6ff27fb..8c27478 100644
--- a/networkcommons/data/omics/scperturb.py
+++ b/networkcommons/data/omics/_scperturb.py
@@ -13,15 +13,21 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+Single-cell RNA-Seq data from the 'scPerturb' resource.
+"""
+
 from __future__ import annotations
 
+__all__ = ['scperturb', 'scperturb_metadata', 'scperturb_datasets']
+
 from typing import Any
 import json
 
 import bs4
 import anndata as ad
 
-from . import common
+from . import _common
 
 _URL = 'https://zenodo.org/record/10044268'
 
@@ -50,7 +56,7 @@ def scperturb_metadata() -> dict[str, Any]:
     record is https://zenodo.org/records/10044268.
     """
 
-    soup = common._open(_URL, ftype = 'html')
+    soup = _common._open(_URL, ftype = 'html')
     data = soup.find(id = 'recordCitation').attrs['data-record']
 
     return json.loads(data)
@@ -72,6 +78,6 @@ def scperturb(dataset: str) -> ad.AnnData:
     """
 
     urls = scperturb_datasets()
-    path = common._maybe_download(urls[dataset])
+    path = _common._maybe_download(urls[dataset])
 
     return ad.read_h5ad(path)
diff --git a/networkcommons/eval/__init__.py b/networkcommons/eval/__init__.py
index a01b238..553fff4 100644
--- a/networkcommons/eval/__init__.py
+++ b/networkcommons/eval/__init__.py
@@ -17,4 +17,4 @@
 Network metrics and analysis methods.
 """
 
-from . import metrics as metrics
+from .metrics import *
diff --git a/networkcommons/eval/metrics.py b/networkcommons/eval/_metrics.py
similarity index 93%
rename from networkcommons/eval/metrics.py
rename to networkcommons/eval/_metrics.py
index 195d249..765a278 100644
--- a/networkcommons/eval/metrics.py
+++ b/networkcommons/eval/_metrics.py
@@ -17,9 +17,7 @@
 Basic graph metrics.
 """
 
-import pandas as pd
-import networkx as nx
-import numpy as np
+from __future__ import annotations
 
 __all__ = [
     'get_number_nodes',
@@ -31,8 +29,12 @@
     'get_graph_metrics',
 ]
 
+import pandas as pd
+import networkx as nx
+import numpy as np
+
 
-def get_number_nodes(network):
+def get_number_nodes(network: nx.Graph) -> int:
     """
     Get the number of nodes in the network.
 
@@ -46,7 +48,7 @@ def get_number_nodes(network):
     return network.number_of_nodes()
 
 
-def get_number_edges(network):
+def get_number_edges(network: nx.Graph) -> int:
     """
     Get the number of edges in the network.
 
@@ -60,7 +62,7 @@ def get_number_edges(network):
     return network.number_of_edges()
 
 
-def get_mean_degree(network):
+def get_mean_degree(network: nx.Graph) -> float:
     """
     Get the mean degree centrality of the network.
 
@@ -74,7 +76,7 @@ def get_mean_degree(network):
     return np.mean(list(dict(nx.degree(network)).values()))
 
 
-def get_mean_betweenness(network):
+def get_mean_betweenness(network: nx.Graph) -> float:
     """
     Get the mean betweenness centrality of the network.
 
@@ -88,7 +90,7 @@ def get_mean_betweenness(network):
     return np.mean(list(nx.betweenness_centrality(network).values()))
 
 
-def get_mean_closeness(network):
+def get_mean_closeness(network: nx.Graph) -> float:
     """
     Get the mean closeness centrality of the network.
 
diff --git a/networkcommons/methods/__init__.py b/networkcommons/methods/__init__.py
index 475fc33..4497219 100644
--- a/networkcommons/methods/__init__.py
+++ b/networkcommons/methods/__init__.py
@@ -17,6 +17,6 @@
 Network based inference methods and network operations.
 """
 
-from networkcommons._methods.graph import *
-from networkcommons._methods.causal import *
-from networkcommons._methods.moon import *
\ No newline at end of file
+from ._graph import *
+from ._causal import *
+from ._moon import *
diff --git a/networkcommons/methods/causal.py b/networkcommons/methods/_causal.py
similarity index 81%
rename from networkcommons/methods/causal.py
rename to networkcommons/methods/_causal.py
index de8594b..a3fff3e 100644
--- a/networkcommons/methods/causal.py
+++ b/networkcommons/methods/_causal.py
@@ -17,19 +17,17 @@
 Causal network inference methods.
 """
 
-import networkx as nx
-import corneto as cn
-from corneto.contrib.networkx import (
-    networkx_to_corneto_graph,
-    corneto_graph_to_networkx
-)
-from corneto.methods.carnival import get_selected_edges
+from __future__ import annotations
 
 __all__ = [
     'convert_cornetograph',
     'run_corneto_carnival',
 ]
 
+import lazy_import
+import networkx as nx
+cn = lazy_import.lazy_import('corneto')
+
 
 def convert_cornetograph(graph):
     """
@@ -44,7 +42,7 @@ def convert_cornetograph(graph):
     if isinstance(graph, cn._graph.Graph):
         corneto_graph = graph
     elif isinstance(graph, (nx.Graph, nx.DiGraph)):
-        corneto_graph = networkx_to_corneto_graph(graph)
+        corneto_graph = cn.contrib.networkx.networkx_to_corneto_graph(graph)
 
     return corneto_graph
 
@@ -80,10 +78,14 @@ def run_corneto_carnival(network,
         verbose=verbose
     )
 
-    network_sol = graph.edge_subgraph(get_selected_edges(problem, graph))
+    network_sol = graph.edge_subgraph(
+        cn.methods.carnival.get_selected_edges(problem, graph),
+    )
 
-    network_nx = corneto_graph_to_networkx(network_sol,
-                                           skip_unsupported_edges=True)
+    network_nx = cn.contrib.networkx.corneto_graph_to_networkx(
+        network_sol,
+        skip_unsupported_edges=True,
+    )
 
     network_nx.remove_nodes_from(['_s', '_pert_c0', '_meas_c0'])
 
diff --git a/networkcommons/methods/graph.py b/networkcommons/methods/_graph.py
similarity index 99%
rename from networkcommons/methods/graph.py
rename to networkcommons/methods/_graph.py
index ff06d49..e10f50c 100644
--- a/networkcommons/methods/graph.py
+++ b/networkcommons/methods/_graph.py
@@ -13,16 +13,12 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+from __future__ import annotations
+
 """
 Graph based methods.
 """
 
-import networkx as nx
-import numpy as np
-
-from networkcommons import _utils
-from networkcommons._session import session as _session
-
 __all__ = [
     'run_shortest_paths',
     'run_sign_consistency',
@@ -33,6 +29,12 @@
     'compute_ppr_overlap',
 ]
 
+import networkx as nx
+import numpy as np
+
+from networkcommons import _utils
+from networkcommons._session import session as _session
+
 
 def run_shortest_paths(network, source_dict, target_dict, verbose=False):
     """
diff --git a/networkcommons/methods/moon.py b/networkcommons/methods/_moon.py
similarity index 99%
rename from networkcommons/methods/moon.py
rename to networkcommons/methods/_moon.py
index 133209a..bc21120 100644
--- a/networkcommons/methods/moon.py
+++ b/networkcommons/methods/_moon.py
@@ -17,16 +17,7 @@
 Moon: multi-omics??
 """
 
-from typing import Counter
-import re
-
-import networkx as nx
-import pandas as pd
-import decoupler as dc
-import numpy as np
-
-from networkcommons._methods import graph as _graph
-from networkcommons._session import _log
+from __future__ import annotations
 
 __all__ = [
     'meta_network_cleanup',
@@ -44,6 +35,18 @@
     'translate_res',
 ]
 
+import collections
+import re
+
+import lazy_import
+import networkx as nx
+import pandas as pd
+dc = lazy_import.lazy_module('decoupler')
+import numpy as np
+
+from . import _graph
+from networkcommons._session import _log
+
 
 def meta_network_cleanup(graph):
     """
@@ -297,7 +300,7 @@ def compress_same_children(uncompressed_graph, sig_input, metab_input):
         if parent not in sig_input and parent not in metab_input
     }
 
-    signature_counts = Counter(filtered_signatures.values())
+    signature_counts = collections.Counter(filtered_signatures.values())
 
     # Identify duplicated signatures that are not in metab_input or sig_input
     duplicated_parents = {
diff --git a/networkcommons/network/__init__.py b/networkcommons/network/__init__.py
index e69de29..e910329 100644
--- a/networkcommons/network/__init__.py
+++ b/networkcommons/network/__init__.py
@@ -0,0 +1,25 @@
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
+"""
+Representation of molecular interaction networks.
+
+The `Network` object represents a graph of molecular interactions with custom
+node and edge attributes and metadata. It is a central piece of the
+`networkcommons` package, and integrates virtually all the functionalities
+provided.
+"""
+
+from ._network import *
diff --git a/networkcommons/network/_network.py b/networkcommons/network/_network.py
index 4425b75..94cf3b6 100644
--- a/networkcommons/network/_network.py
+++ b/networkcommons/network/_network.py
@@ -1,24 +1,63 @@
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
+"""
+Representation of molecular interaction networks.
+
+The `Network` object represents a graph of molecular interactions with custom
+node and edge attributes and metadata. It is a central piece of the
+`networkcommons` package, and integrates virtually all the functionalities
+provided.
+"""
+
 from __future__ import annotations
 
+__all__ = ['Network']
+
+import lazy_import
 import pandas as pd
-import corneto
+cn = lazy_import.lazy_import('corneto')
 
-from networkcommons._data import _network as _universe
-from networkcommons._noi._noi import Noi
+from networkcommons.data import _network as _universe
+from networkcommons.noi._noi import Noi
 
 
 class Network:
+    """
+    A molecular interaction network.
+    """
 
-    _co: corneto.Graph
-    _edges: pd.DataFrame
-    _nodes: pd.DataFrame
 
     def __init__(
         self,
         universe: str | None = "omnipath",
         noi: Noi | list[str] | list[list[str]] | dict[str, list[str]] = None,
     ):
+        """
+        Args:
+            universe:
+                The prior knowledge universe: a complete set of interactions
+                that the instance uses to extract subnetworks from and that
+                will be queried in operations applied on the instance.
+            noi:
+                Nodes of interest.
+        """
 
+        self._co: cn.Graph = None
+        self._edges: pd.DataFrame = None
+        self._nodes: pd.DataFrame = None
         self.universe = universe
         self.noi = noi
 
@@ -43,7 +82,7 @@ def as_nx(self, attrs: str | list[str]) -> nx.DiGraph:
         pass
 
 
-    def as_corneto(self, attrs: str | list[str]) -> corneto.Graph:
+    def as_corneto(self, attrs: str | list[str]) -> cn.Graph:
         """
         Return the graph as an igraph object with the desired attributes.
         """
diff --git a/networkcommons/noi/__init__.py b/networkcommons/noi/__init__.py
index 31bfd8a..6843acb 100644
--- a/networkcommons/noi/__init__.py
+++ b/networkcommons/noi/__init__.py
@@ -13,5 +13,11 @@
 # https://www.gnu.org/licenses/gpl-3.0.txt
 #
 
+"""
+Handling nodes of interest for network lookup queries.
+"""
+
+__all__ = ['Node', 'Noi']
+
 from ._node import Node
 from ._noi import Noi
diff --git a/networkcommons/noi/_node.py b/networkcommons/noi/_node.py
index c2399b4..b4e89f0 100644
--- a/networkcommons/noi/_node.py
+++ b/networkcommons/noi/_node.py
@@ -19,18 +19,19 @@
 
 from __future__ import annotations
 
+__all__ = ['Node']
+
 from typing import Generator, Literal, Sequence
 import re
 import inspect
 
-import pypath_common._misc as _common
-import pypath.utils.taxonomy as _taxonomy
-import pypath.utils.mapping as _mapping
-import pypath.utils.orthology as _orthology
-import pypath.inputs.uniprot as _uniprot
-import pypath.inputs.uniprot_db as _uniprot_db
-
-__all__ = ['Node']
+import lazy_import
+_common = lazy_import.lazy_module('pypath_common._misc')
+_taxonomy = lazy_import.lazy_module('pypath.utils.taxonomy')
+_mapping = lazy_import.lazy_module('pypath.utils.mapping')
+_orthology = lazy_import.lazy_module('pypath.utils.orthology')
+_uniprot = lazy_import.lazy_module('pypath.inputs.uniprot')
+_uniprot_db = lazy_import.lazy_module('pypath.inputs.uniprot_db')
 
 
 _REENS = re.compile(r'ENS[A-Z]*?([A-Z])[0-9]+')
diff --git a/networkcommons/noi/_noi.py b/networkcommons/noi/_noi.py
index bbfe39a..2cb864e 100644
--- a/networkcommons/noi/_noi.py
+++ b/networkcommons/noi/_noi.py
@@ -19,6 +19,8 @@
 
 from __future__ import annotations
 
+__all__ = ['Noi']
+
 from typing import Any, Callable, Hashable
 import collections
 import itertools
@@ -30,7 +32,6 @@
 
 from . import _node
 
-__all__ = ['Noi']
 
 class Noi(collections.abc.Mapping):
 
diff --git a/networkcommons/visual/__init__.py b/networkcommons/visual/__init__.py
index 122425f..756899b 100644
--- a/networkcommons/visual/__init__.py
+++ b/networkcommons/visual/__init__.py
@@ -17,9 +17,9 @@
 Visualization methods for networks and analyses.
 """
 
-from . import vis_networkx as vis_networkx
-from . import vis_yfiles as vis_yfiles
-from . import styles as vis_styles
-from . import yfiles_styles as vis_yfiles_styles
-from . import rnaseq as vis_rnaseq
-from . import network_stats as vis_network_stat
+from ._vis_networkx import *
+from ._vis_yfiles import *
+from ._styles import *
+from ._yfiles_styles import *
+from ._rnaseq import *
+from ._network_stats import *
diff --git a/networkcommons/visual/_aux.py b/networkcommons/visual/_aux.py
index b15d4bf..1a05d89 100644
--- a/networkcommons/visual/_aux.py
+++ b/networkcommons/visual/_aux.py
@@ -1,3 +1,18 @@
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
 
 def wrap_node_name(node_name):
     if ":" in node_name:
@@ -7,5 +22,3 @@ def wrap_node_name(node_name):
         return node_name[8:]
     else:
         return node_name
-
-
diff --git a/networkcommons/visual/network_stats.py b/networkcommons/visual/_network_stats.py
similarity index 87%
rename from networkcommons/visual/network_stats.py
rename to networkcommons/visual/_network_stats.py
index 22a8c57..3359332 100644
--- a/networkcommons/visual/network_stats.py
+++ b/networkcommons/visual/_network_stats.py
@@ -1,7 +1,32 @@
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
+"""
+Plot network (graph) metrics.
+"""
+
+from __future__ import annotations
+
+__all__  = ['plot_n_nodes_edges']
+
+from typing import List, Dict
+
+import lazy_import
 import pandas as pd
-import matplotlib.pyplot as plt
+plt = lazy_import.lazy_import('matplotlib.pyplot')
 import networkx as nx
-from typing import List, Dict
 
 
 def plot_n_nodes_edges(
@@ -97,4 +122,4 @@ def plot_n_nodes_edges(
         plt.savefig(filepath)
 
     if render:
-        plt.show()
\ No newline at end of file
+        plt.show()
diff --git a/networkcommons/visual/rnaseq.py b/networkcommons/visual/_rnaseq.py
similarity index 85%
rename from networkcommons/visual/rnaseq.py
rename to networkcommons/visual/_rnaseq.py
index 3921d66..d0e359d 100644
--- a/networkcommons/visual/rnaseq.py
+++ b/networkcommons/visual/_rnaseq.py
@@ -1,9 +1,37 @@
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
+"""
+Plots for omics data exploration.
+"""
+
+from __future__ import annotations
+
+__all__  = [
+    'build_volcano_plot',
+    'build_ma_plot',
+    'build_pca_plot',
+    'build_heatmap_with_tree',
+]
+
+import lazy_import
 import pandas as pd
 import numpy as np
-import matplotlib.pyplot as plt
-import seaborn as sns
-from sklearn.decomposition import PCA
-from typing import List
+plt = lazy_import.lazy_import('matplotlib.pyplot')
+sns = lazy_import.lazy_import('seaborn')
+sklearn_decomp = lazy_import.lazy_module('sklearn.decomposition')
 
 
 def build_volcano_plot(
@@ -135,7 +163,7 @@ def build_pca_plot(
         save: bool = False,
         output_dir: str = "."
 ):
-    pca = PCA(n_components=2)
+    pca = sklearn_decomp.PCA(n_components=2)
     principal_components = pca.fit_transform(data)
     pca_df = pd.DataFrame(data=principal_components, columns=['PC1', 'PC2'])
 
@@ -162,7 +190,7 @@ def build_heatmap_with_tree(
         data: pd.DataFrame,
         top_n: int = 50,
         value_column: str = 'log2FoldChange_condition_1',
-        conditions: List[str] = None,
+        conditions: list[str] = None,
         title: str = "Heatmap of Top Differentially Expressed Genes",
         save: bool = False,
         output_dir: str = "."
@@ -174,7 +202,7 @@ def build_heatmap_with_tree(
         data (pd.DataFrame): DataFrame containing RNA-seq results.
         top_n (int): Number of top differentially expressed genes to include in the heatmap.
         value_column (str): Column name for the values to rank and select the top genes.
-        conditions (List[str]): List of condition columns to include in the heatmap.
+        conditions (list[str]): List of condition columns to include in the heatmap.
         title (str): Title of the plot.
         save (bool): Whether to save the plot. Default is False.
         output_dir (str): Directory to save the plot. Default is ".".
@@ -196,4 +224,4 @@ def build_heatmap_with_tree(
     if save:
         plt.savefig(f"{output_dir}/heatmap_with_tree.png")
 
-    plt.show()
\ No newline at end of file
+    plt.show()
diff --git a/networkcommons/visual/styles.py b/networkcommons/visual/_styles.py
similarity index 91%
rename from networkcommons/visual/styles.py
rename to networkcommons/visual/_styles.py
index 54e7838..04872a0 100644
--- a/networkcommons/visual/styles.py
+++ b/networkcommons/visual/_styles.py
@@ -1,3 +1,26 @@
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
+"""
+Style definitions for network visualizations.
+"""
+
+from __future__ import annotations
+
+__all__  = ['get_styles', 'merge_styles', 'set_style_attributes']
+
 from networkcommons._session import _log
 
 
@@ -156,4 +179,3 @@ def merge_styles(default_style, custom_style, path=""):
                 _log(f"Missing key '{path}.{key}' in custom style. Using default value.")
 
     return merged_style
-
diff --git a/networkcommons/visual/vis_networkx.py b/networkcommons/visual/_vis_networkx.py
similarity index 82%
rename from networkcommons/visual/vis_networkx.py
rename to networkcommons/visual/_vis_networkx.py
index 7dae8f0..88b7e48 100644
--- a/networkcommons/visual/vis_networkx.py
+++ b/networkcommons/visual/_vis_networkx.py
@@ -14,19 +14,28 @@
 #
 
 """
-This module contains functions to visualize networks.
-The styles for different types of networks are defined in the get_styles() function.
-The set_style_attributes() function is used to set attributes for nodes and edges based on the given styles.
-The visualize_network_default() function visualizes the graph with default style.
-The visualize_network_sign_consistent() function visualizes the graph considering sign consistency.
-The visualize_network() function is the main function to visualize the graph based on the network type.
+Visualize networks.
+
+The styles for different types of networks are defined in the `get_styles()`
+function.  The `set_style_attributes()` function is used to set attributes for
+nodes and edges based on the given styles.  The `visualize_network_default()`
+function visualizes the graph with default style.  The
+`visualize_network_sign_consistent()` function visualizes the graph considering
+sign consistency.  The `visualize_network()` function is the main function to
+visualize the graph based on the network type.
 """
 
+from __future__ import annotations
+
+__all__ = ['NetworkXVisualizer']
+
+import lazy_import
 import networkx as nx
-import matplotlib.pyplot as plt
-from networkcommons._visual._aux import wrap_node_name
+plt = lazy_import.lazy_import('matplotlib.pyplot')
+
+from . import _aux
+from . import _styles
 from networkcommons._session import _log
-from networkcommons._visual.styles import (get_styles, set_style_attributes, merge_styles)
 
 
 class NetworkXVisualizer:
@@ -34,13 +43,13 @@ class NetworkXVisualizer:
     def __init__(self, network, color_by="effect"):
         self.network = network.copy()
         self.color_by = color_by
-        self.edge_colors = get_styles()['default']['edges']
+        self.edge_colors = _styles.get_styles()['default']['edges']
 
     def set_custom_edge_colors(self, custom_edge_colors):
         self.edge_colors.update(custom_edge_colors)
 
     def color_nodes(self):
-        default_node_colors = get_styles()['default']['nodes']['default']
+        default_node_colors = _styles.get_styles()['default']['nodes']['default']
         source_node_color = default_node_colors['sources']
         target_node_color = default_node_colors['targets']
         nodes = self.network.nodes
@@ -54,7 +63,7 @@ def color_nodes(self):
                 nodes[node]['color'] = target_node_color
 
     def color_edges(self):
-        edge_colors = get_styles()['default']['edges']
+        edge_colors = _styles.get_styles()['default']['edges']
         for edge in self.network.edges:
             u, v = edge
             edge_data = self.network.get_edge_data(u, v)
@@ -80,8 +89,8 @@ def visualize_network_default(self,
             prog (str, optional): The layout program to use. Defaults to 'dot'.
             custom_style (dict, optional): The custom style to apply. If None, the default style is used.
         """
-        default_style = get_styles()['default']
-        style = merge_styles(default_style, custom_style)
+        default_style = _styles.get_styles()['default']
+        style = _styles.merge_styles(default_style, custom_style)
 
         A = nx.nx_agraph.to_agraph(network)
         A.graph_attr['ratio'] = '1.2'
@@ -100,11 +109,11 @@ def visualize_network_default(self,
             else:
                 base_style = style['nodes']['other']
 
-            set_style_attributes(node, base_style)
+            _styles.set_style_attributes(node, base_style)
 
         for edge in A.edges():
             edge_style = style['edges']['neutral']
-            set_style_attributes(edge, edge_style)
+            _styles.set_style_attributes(edge, edge_style)
 
         A.layout(prog=prog)
         return A
@@ -125,8 +134,8 @@ def visualize_network_sign_consistent(self,
             prog (str, optional): The layout program to use. Defaults to 'dot'.
             custom_style (dict, optional): The custom style to apply. Defaults to None.
         """
-        default_style = get_styles()['sign_consistent']
-        style = merge_styles(default_style, custom_style)
+        default_style = _styles.get_styles()['sign_consistent']
+        style = _styles.merge_styles(default_style, custom_style)
 
         # Call the core visualization function
         A = self.visualize_network_default(network, source_dict, target_dict, prog, style)
@@ -153,7 +162,7 @@ def visualize_network_sign_consistent(self,
 
             if condition_style:
                 # Apply condition style without overwriting base style
-                set_style_attributes(node, {}, condition_style)
+                _styles.set_style_attributes(node, {}, condition_style)
 
         for edge in A.edges():
             u, v = edge
@@ -168,7 +177,7 @@ def visualize_network_sign_consistent(self,
             else:
                 edge_style = style['edges']['neutral']
 
-            set_style_attributes(edge, edge_style)
+            s_styles.et_style_attributes(edge, edge_style)
 
         return A
 
@@ -193,7 +202,7 @@ def visualize_network(self,
         if network_type == 'sign_consistent':
             return self.visualize_network_sign_consistent(network, source_dict, target_dict, prog, custom_style)
         else:
-            default_style = get_styles().get(network_type, get_styles()['default'])
+            default_style = _styles.get_styles().get(network_type, get_styles()['default'])
             return self.visualize_network_default(network, source_dict, target_dict, prog, custom_style)
 
     def visualize(self, output_file='network.png', render=False, highlight_nodes=None, style=None):
@@ -211,7 +220,7 @@ def visualize(self, output_file='network.png', render=False, highlight_nodes=Non
                 highlight_color = style['highlight_color']
             else:
                 highlight_color = style['nodes']['default']['fillcolor']
-            highlight_nodes = [wrap_node_name(node) for node in highlight_nodes]
+            highlight_nodes = [_aux.wrap_node_name(node) for node in highlight_nodes]
             nx.draw_networkx_nodes(self.network, pos, nodelist=highlight_nodes, node_color=highlight_color)
 
         if render:
diff --git a/networkcommons/visual/vis_yfiles.py b/networkcommons/visual/_vis_yfiles.py
similarity index 64%
rename from networkcommons/visual/vis_yfiles.py
rename to networkcommons/visual/_vis_yfiles.py
index f1cf616..3a7fa9a 100644
--- a/networkcommons/visual/vis_yfiles.py
+++ b/networkcommons/visual/_vis_yfiles.py
@@ -1,36 +1,58 @@
-from yfiles_jupyter_graphs import GraphWidget
-from typing import Dict
-from IPython.display import display
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
+"""
+Interactive network visualization using the yFiles HTML widget.
+"""
+
+from __future__ import annotations
+
+__all__ = ['YFilesVisualizer']
+
+import lazy_import
+yfiles = lazy_import.lazy_module('yfiles_jupyter_graphs')
+ipydisplay = lazy_import.lazy_module('IPython.display')
+
+from . import _yfiles_styles
 from networkcommons._session import _log
 
-from networkcommons._visual.yfiles_styles import (get_styles,
-                                                  apply_node_style,
-                                                  apply_edge_style,
-                                                  update_node_property,
-                                                  update_edge_property,
-                                                  get_edge_color,
-                                                  get_comparison_color)
-
 
 class YFilesVisualizer:
 
+
     def __init__(self, network):
+
         self.network = network.copy()
-        self.styles = get_styles()
+        self.styles = _yfiles_styles.get_styles()
+
 
     def visualize(self, graph_layout="Organic", directed=True):
+
         available_layouts = ["Circular", "Hierarchic", "Organic", "Orthogonal", "Radial", "Tree"]
         if graph_layout not in available_layouts:
             graph_layout = "Organic"
             _log.warning(f"Graph layout not available. Using default layout: {graph_layout}")
 
         # creating empty object for visualization
-        w = GraphWidget()
+        w = yfiles.GraphWidget()
 
         # filling w with nodes
         node_objects = []
 
         for node in self.network.nodes:
+
             styled_node = self.styles['default']['nodes']
             node_objects.append({
                 "id": node,
@@ -45,8 +67,9 @@ def visualize(self, graph_layout="Organic", directed=True):
         edge_objects = []
 
         for edge in self.network.edges(data=True):
+
             styled_edge = self.styles['default']['edges']
-            styled_edge = {"color": get_edge_color(edge[2]['sign'], self.styles)}
+            styled_edge = {"color": _yfiles_styles.get_edge_color(edge[2]['sign'], self.styles)}
             edge_objects.append({
                 "id": (edge[0], edge[1]),
                 "start": edge[0],
@@ -64,18 +87,21 @@ def visualize(self, graph_layout="Organic", directed=True):
         w.directed = directed
         w.graph_layout = graph_layout
 
-        display(w)
+        ipydisplay.display(w)
 
     def vis_comparison(self, int_comparison, node_comparison, graph_layout, directed):
         # creating empty object for visualization
-        w = GraphWidget()
+        w = yfiles.GraphWidget()
 
         objects = []
         for idx, item in node_comparison.iterrows():
             node_props = {"label": item["node"], "comparison": item["comparison"]}
-            node = apply_node_style(node_props, self.styles['default']['nodes'])
-            node = update_node_property(node, type="color",
-                                        value=get_comparison_color(item["comparison"], self.styles))
+            node = _yfiles_styles.apply_node_style(node_props, self.styles['default']['nodes'])
+            node = _yfiles_styles.update_node_property(
+                node,
+                type="color",
+                value=_yfiles_styles.get_comparison_color(item["comparison"], self.styles),
+            )
             objects.append({
                 "id": item["node"],
                 "properties": node,
@@ -87,9 +113,12 @@ def vis_comparison(self, int_comparison, node_comparison, graph_layout, directed
         objects = []
         for index, row in int_comparison.iterrows():
             edge_props = {"comparison": row["comparison"]}
-            edge = apply_edge_style(edge_props, self.styles['default']['edges'])
-            edge = update_edge_property(edge, type="color",
-                                        value=get_comparison_color(row["comparison"], self.styles))
+            edge = _yfiles_styles.apply_edge_style(edge_props, self.styles['default']['edges'])
+            edge = _yfiles_styles.update_edge_property(
+                edge,
+                type="color",
+                value=_yfiles_styles.get_comparison_color(row["comparison"], self.styles),
+            )
             objects.append({
                 "id": row["comparison"],
                 "start": row["source"],
@@ -109,19 +138,19 @@ def vis_comparison(self, int_comparison, node_comparison, graph_layout, directed
         display(w)
 
     @staticmethod
-    def custom_edge_color_mapping(edge: Dict):
+    def custom_edge_color_mapping(edge: dict):
         return edge["properties"]["color"]
 
     @staticmethod
-    def custom_node_color_mapping(node: Dict):
+    def custom_node_color_mapping(node: dict):
         return {"color": node["color"]}
 
     @staticmethod
-    def custom_factor_mapping(node: Dict):
+    def custom_factor_mapping(node: dict):
         return 1
 
     @staticmethod
-    def custom_label_styles_mapping(node: Dict):
-        label_style = get_styles()['default']['labels'].copy()
+    def custom_label_styles_mapping(node: dict):
+        label_style = _yfiles_styles.get_styles()['default']['labels'].copy()
         label_style['text'] = node["properties"]["label"]
         return label_style
diff --git a/networkcommons/visual/yfiles_styles.py b/networkcommons/visual/_yfiles_styles.py
similarity index 86%
rename from networkcommons/visual/yfiles_styles.py
rename to networkcommons/visual/_yfiles_styles.py
index 9cc4844..03829a2 100644
--- a/networkcommons/visual/yfiles_styles.py
+++ b/networkcommons/visual/_yfiles_styles.py
@@ -1,3 +1,35 @@
+#!/usr/bin/env python
+
+#
+# This file is part of the `networkcommons` Python module
+#
+# Copyright 2024
+# Heidelberg University Hospital
+#
+# File author(s): Saez Lab (omnipathdb@gmail.com)
+#
+# Distributed under the GPLv3 license
+# See the file `LICENSE` or read a copy at
+# https://www.gnu.org/licenses/gpl-3.0.txt
+#
+
+"""
+Interactive network visualization using the yFiles HTML widget.
+"""
+
+from __future__ import annotations
+
+__all__ = [
+    'get_styles',
+    'get_comparison_color',
+    'get_edge_color',
+    'update_node_property',
+    'update_edge_property',
+    'apply_node_style',
+    'apply_edge_style',
+]
+
+
 def get_styles():
     """
     Return a dictionary containing styles for different types of networks specific to yFiles visualizations.