diff --git a/CHANGES.md b/CHANGES.md
index 727f1e54..0c156ce1 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,7 +1,15 @@
 # Release notes
 
 See also the
-[unreleased changes](https://foss.heptapod.net/fluiddyn/fluidimage/-/compare/0.4.2...branch%2Fdefault).
+[unreleased changes](https://foss.heptapod.net/fluiddyn/fluidimage/-/compare/0.4.3...branch%2Fdefault).
+
+## [0.4.3] (2024-03-27)
+
+- [!85](https://foss.heptapod.net/fluiddyn/fluidimage/-/merge_requests/85): `fluidpivviewer`.
+- [!84](https://foss.heptapod.net/fluiddyn/fluidimage/-/merge_requests/84): `multi_exec_async`
+  using {class}`fluidimage.topologies.splitters.Splitter`.
+- Other bugfixes and improvements (name PIV files and
+  {class}`fluidimage.postproc.vector_field.VectorFieldOnGrid`).
 
 ## [0.4.2] (2024-03-20)
 
@@ -168,3 +176,4 @@ This version contains incompatible API changes documented here.
 [0.4.0]: https://foss.heptapod.net/fluiddyn/fluidimage/-/compare/0.3.0...0.4.0
 [0.4.1]: https://foss.heptapod.net/fluiddyn/fluidimage/-/compare/0.4.0...0.4.1
 [0.4.2]: https://foss.heptapod.net/fluiddyn/fluidimage/-/compare/0.4.1...0.4.2
+[0.4.3]: https://foss.heptapod.net/fluiddyn/fluidimage/-/compare/0.4.2...0.4.3
diff --git a/doc/conf.py b/doc/conf.py
index c54b180a..17542e78 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -13,18 +13,13 @@
 
 import os
 
-os.environ["OMP_NUM_THREADS"] = "1"
-
 import fluidimage
 
-# we want this module to be importable.
-try:
-    import fluidimage.topologies.optical_flow
-except Exception:
-    import traceback
-
-    traceback.print_exc()
+# we want these modules to be importable.
+import fluidimage.topologies.preproc
+import fluidimage.topologies.optical_flow
 
+os.environ["OMP_NUM_THREADS"] = "1"
 # -- General configuration ----------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
diff --git a/doc/examples/piv_parallel.py b/doc/examples/piv_parallel.py
index 30cbbc61..f8f2ebf2 100644
--- a/doc/examples/piv_parallel.py
+++ b/doc/examples/piv_parallel.py
@@ -5,11 +5,17 @@
 
 params.series.path = get_path_image_samples() / "Karman/Images"
 
+params.mask.strcrop = "50:350, 0:380"
+
 params.piv0.shape_crop_im0 = 32
-params.multipass.number = 2
-params.multipass.use_tps = False
+params.piv0.displacement_max = 5
+params.piv0.nb_peaks_to_search = 2
 
-params.mask.strcrop = ":, 50:500"
+params.fix.correl_min = 0.4
+params.fix.threshold_diff_neighbour = 2.0
+
+params.multipass.number = 2
+params.multipass.use_tps = "last"
 
 # params.saving.how = 'complete'
 params.saving.postfix = "piv_example"
diff --git a/doc/examples/piv_try_params.py b/doc/examples/piv_try_params.py
index 8d1f62c8..1fa40400 100644
--- a/doc/examples/piv_try_params.py
+++ b/doc/examples/piv_try_params.py
@@ -4,20 +4,18 @@
 
 params = Work.create_default_params()
 
-params.multipass.number = 2
-params.multipass.use_tps = True
+params.series.path = "../../image_samples/Oseen/Images"
+
+params.mask.strcrop = "30:250, 100:"
 
 params.piv0.shape_crop_im0 = 32
 params.piv0.displacement_max = 5
+
 params.fix.correl_min = 0.2
 params.fix.threshold_diff_neighbour = 8
 
-params.mask.strcrop = "30:250, 100:"
-
-path = "../../image_samples/Oseen/Images"
-# path = '../../image_samples/Karman/Images'
-params.series.path = path
-params.series.str_subset = "i+1:i+3"
+params.multipass.number = 2
+params.multipass.use_tps = True
 
 work = Work(params=params)
 
diff --git a/doc/examples/piv_try_params_Karman.py b/doc/examples/piv_try_params_Karman.py
new file mode 100644
index 00000000..524b6b42
--- /dev/null
+++ b/doc/examples/piv_try_params_Karman.py
@@ -0,0 +1,28 @@
+"""To be run in IPython to find a good set of parameters"""
+
+from fluidimage.piv import Work
+
+params = Work.create_default_params()
+
+params.series.path = "../../image_samples/Karman/Images"
+
+params.mask.strcrop = "50:350, 0:380"
+
+params.fix.correl_min = 0.4
+params.fix.threshold_diff_neighbour = 2.0
+
+params.piv0.shape_crop_im0 = 32
+params.piv0.displacement_max = 5
+params.piv0.nb_peaks_to_search = 2
+
+params.multipass.number = 2
+params.multipass.use_tps = "last"
+
+work = Work(params=params)
+
+piv = work.process_1_serie()
+
+# piv.display(show_interp=True, scale=0.3, show_error=False)
+piv.display(show_interp=False, scale=1, show_error=True)
+
+# piv.save()
diff --git a/doc/tutorials/tuto_piv.md b/doc/tutorials/tuto_piv.md
index cbbd1c1c..1df3e1fc 100644
--- a/doc/tutorials/tuto_piv.md
+++ b/doc/tutorials/tuto_piv.md
@@ -66,9 +66,17 @@ the input images:
 path_src = get_path_image_samples() / "Karman/Images"
 params.series.path = str(path_src)
 
-params.piv0.shape_crop_im0 = 64
+params.mask.strcrop = "50:350, 0:400"
+
+params.piv0.shape_crop_im0 = 48
+params.piv0.displacement_max = 5
+params.piv0.nb_peaks_to_search = 2
+
+params.fix.correl_min = 0.4
+params.fix.threshold_diff_neighbour = 2.0
+
 params.multipass.number = 2
-params.multipass.use_tps = False
+params.multipass.use_tps = "last"
 ```
 
 After instantiating the `Work` class,
@@ -204,15 +212,23 @@ params.saving._print_doc()
 path_src = get_path_image_samples() / "Karman/Images"
 params.series.path = str(path_src)
 
-params.piv0.shape_crop_im0 = 64
+params.mask.strcrop = "50:350, 0:400"
+
+params.piv0.shape_crop_im0 = 48
+params.piv0.displacement_max = 5
+params.piv0.nb_peaks_to_search = 2
+
+params.fix.correl_min = 0.4
+params.fix.threshold_diff_neighbour = 2.0
+
 params.multipass.number = 2
-params.multipass.use_tps = False
+params.multipass.use_tps = "last"
 
 params.saving.how = 'recompute'
 params.saving.postfix = "doc_piv_ipynb"
 ```
 
-In order to run the PIV computation, we have to instanciate an object of the class
+In order to run the PIV computation, we have to instantiate an object of the class
 {class}`fluidimage.piv.Topology`.
 
 ```{code-cell} ipython3
@@ -243,6 +259,13 @@ path_src
 topology.path_dir_result
 ```
 
+```{code-cell} ipython3
+sorted(path.name for path in topology.path_dir_result.glob("*"))
+```
+
+Fluidimage provides the command `fluidpivviewer`, which starts a very simple GUI to
+visualize the PIV results.
+
 ## Analyzing the computation
 
 ```{code-cell} ipython3
diff --git a/image_samples/Milestone/piv_0001a-b.h5 b/image_samples/Milestone/piv_0001a-b.h5
new file mode 120000
index 00000000..5497784e
--- /dev/null
+++ b/image_samples/Milestone/piv_0001a-b.h5
@@ -0,0 +1 @@
+./piv_0000a-b.h5
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
index 5ebe9be5..bf46b0ac 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,7 +9,7 @@ build-backend = 'mesonpy'
 
 [project]
 name = "fluidimage"
-version = "0.4.2"
+version = "0.4.3"
 description = "Fluid image processing with Python."
 authors = [
     {name = "Pierre Augier", email = "pierre.augier@legi.cnrs.fr"},
@@ -55,6 +55,7 @@ Homepage = "https://foss.heptapod.net/fluiddyn/fluidimage"
 fluidimviewer-pg = "fluidimage.gui.pg_main:main"
 fluidimviewer = "fluidimage.gui.imviewer:main"
 fluidimlauncher = "fluidimage.gui.launcher.main:main"
+fluidpivviewer = "fluidimage.gui.piv_viewer:main"
 
 [project.optional-dependencies]
 pims = ["pims"]
diff --git a/src/fluidimage/__init__.py b/src/fluidimage/__init__.py
index 0e9fc39e..96b9500f 100644
--- a/src/fluidimage/__init__.py
+++ b/src/fluidimage/__init__.py
@@ -65,6 +65,10 @@ def get_path_image_samples():
     if path_image_samples.exists():
         return path_image_samples.resolve()
 
+    path_image_samples = Path.home() / "dev/fluidimage/image_samples"
+    if path_image_samples.exists():
+        return path_image_samples
+
     # Gitlab and Github CI
     for name_env_var_project_dir in ("CI_PROJECT_DIR", "GITHUB_WORKSPACE"):
         ci_project_dir = os.getenv(name_env_var_project_dir)
diff --git a/src/fluidimage/gui/__init__.py b/src/fluidimage/gui/__init__.py
index 1fb4452b..24a81e5f 100644
--- a/src/fluidimage/gui/__init__.py
+++ b/src/fluidimage/gui/__init__.py
@@ -9,8 +9,10 @@
 .. autosummary::
    :toctree:
 
+   base_matplotlib
    imviewer
    launcher
    pg_main
+   piv_viewer
 
 """
diff --git a/src/fluidimage/gui/base_matplotlib.py b/src/fluidimage/gui/base_matplotlib.py
new file mode 100644
index 00000000..487d13f9
--- /dev/null
+++ b/src/fluidimage/gui/base_matplotlib.py
@@ -0,0 +1,32 @@
+"""Base class using matplotlib widgets
+
+"""
+
+from matplotlib.widgets import Button, TextBox
+
+
+class AppMatplotlibWidgets:
+
+    _buttons: dict
+    _textboxes: dict
+
+    def __init__(self):
+        self._buttons = {}
+        self._textboxes = {}
+
+    def _create_button(self, fig, rect, text, func):
+        ax = fig.add_axes(rect)
+        button = Button(ax, text)
+        button.on_clicked(func)
+        self._buttons[text] = button
+        return button
+
+    def _create_text_box(self, fig, rect, name, func, initial):
+        ax = fig.add_axes(rect)
+        textbox = TextBox(ax, name, initial=initial)
+        textbox.on_submit(func)
+        self._textboxes[name] = textbox
+        return textbox
+
+    def get_textbox(self, key):
+        return self._textboxes[key]
diff --git a/src/fluidimage/gui/imviewer.py b/src/fluidimage/gui/imviewer.py
index 5419b6dc..dd93e679 100644
--- a/src/fluidimage/gui/imviewer.py
+++ b/src/fluidimage/gui/imviewer.py
@@ -14,11 +14,11 @@
 from glob import glob
 
 import matplotlib.pyplot as plt
-from matplotlib.widgets import Button, TextBox
 
 from fluiddyn.io.image import imread
 from fluiddyn.util import time_as_str
 from fluiddyn.util.serieofarrays import SerieOfArraysFromFiles
+from fluidimage.gui.base_matplotlib import AppMatplotlibWidgets
 from fluidimage.util import safe_eval
 
 extensions = ["png", "tif", "tiff", "jpg", "jpeg", "bmp", "cine"]
@@ -66,7 +66,7 @@ def parse_args():
     return parser.parse_args()
 
 
-class ImageViewer:
+class ImageViewer(AppMatplotlibWidgets):
     """Simple Image viewer."""
 
     def __init__(self, args):
@@ -98,8 +98,7 @@ def __init__(self, args):
         self.nb_images = len(self.path_files)
         print(f"Will use {self.nb_images} images in the dir {path_dir}")
 
-        self._buttons = {}
-        self._textboxes = {}
+        super().__init__()
 
         fig = self.fig = plt.figure()
         fig.canvas.manager.set_window_title(
@@ -133,14 +132,12 @@ def __init__(self, args):
         function_buttons[3] = self._increase_ifile_n
 
         y = size_button / 3.0
-        for i, x in enumerate(x_buttons):
-            name = name_buttons[i]
-            func = function_buttons[i]
+        for x, name, func in zip(x_buttons, name_buttons, function_buttons):
             self._create_button(fig, [x, y, size_button, size_button], name, func)
 
         self._n = 1
 
-        self._create_text(
+        self._create_text_box(
             fig,
             [0.1, y, 2 * size_button, size_button],
             "n = ",
@@ -148,7 +145,7 @@ def __init__(self, args):
             "1",
         )
 
-        self._create_text(
+        self._create_text_box(
             fig,
             [0.87, 0.92, 1.5 * size_button, size_button],
             "cmax = ",
@@ -156,7 +153,7 @@ def __init__(self, args):
             "{:.2f}".format(self.clim[1]),
         )
 
-        self._create_text(
+        self._create_text_box(
             fig,
             [0.87, 0.1, 1.5 * size_button, size_button],
             "cmin = ",
@@ -235,20 +232,6 @@ def change_im(self):
         print("\rchanged to file " + name_file + " " * 20)
         self._image_changing = False
 
-    def _create_button(self, fig, rect, text, func):
-        ax = fig.add_axes(rect)
-        button = Button(ax, text)
-        button.on_clicked(func)
-        self._buttons[text] = button
-        return button
-
-    def _create_text(self, fig, rect, name, func, initial):
-        ax = fig.add_axes(rect)
-        textbox = TextBox(ax, name, initial=initial)
-        textbox.on_submit(func)
-        self._textboxes[name] = textbox
-        return textbox
-
     def _switch(self):
         if self._last_was_increase:
             self._decrease_ifile_n()
diff --git a/src/fluidimage/gui/meson.build b/src/fluidimage/gui/meson.build
index ec28bc3b..2b204cce 100644
--- a/src/fluidimage/gui/meson.build
+++ b/src/fluidimage/gui/meson.build
@@ -1,11 +1,14 @@
 
 python_sources = [
   '__init__.py',
+  'base_matplotlib.py',
   'imviewer.py',
   'pg_main.py',
   'pg_wrapper.py',
+  'piv_viewer.py',
   'test_imviewer.py',
   'test_imviewer_pg.py',
+  'test_piv_viewer.py',
 ]
 
 py.install_sources(
diff --git a/src/fluidimage/gui/piv_viewer.py b/src/fluidimage/gui/piv_viewer.py
new file mode 100644
index 00000000..bcc13dce
--- /dev/null
+++ b/src/fluidimage/gui/piv_viewer.py
@@ -0,0 +1,211 @@
+"""PIV viewer
+
+Coded with matplotlib GUI!
+
+.. autoclass:: VectorFieldsViewer
+   :members:
+   :private-members:
+
+"""
+
+import argparse
+import os
+import sys
+from pathlib import Path
+
+import h5py
+import matplotlib.pyplot as plt
+
+from fluiddyn.util.serieofarrays import SerieOfArraysFromFiles
+from fluidimage.gui.base_matplotlib import AppMatplotlibWidgets
+
+size_button = 0.06
+sep_button = 0.02
+x0 = 0.5
+
+name_buttons = ["-1", "+1"]
+
+x_buttons = [
+    x0 + i * (size_button + sep_button) for i in range(len(name_buttons))
+]
+
+
+def get_piv_data_from_path(path):
+
+    with h5py.File(path, "r") as file:
+        class_name = file.attrs["class_name"]
+        module_name = file.attrs["module_name"]
+
+    if isinstance(class_name, bytes):
+        class_name = class_name.decode()
+        module_name = module_name.decode()
+
+    if (
+        class_name in ("MultipassPIVResults", "LightPIVResults")
+        and module_name == "fluidimage.data_objects.piv"
+    ):
+        if class_name == "MultipassPIVResults":
+            with h5py.File(path, "r") as file:
+                keys = sorted(key for key in file.keys() if key.startswith("piv"))
+            key_piv = keys[-1]
+        else:
+            key_piv = "piv"
+
+        with h5py.File(path, "r") as file:
+            piv = file[key_piv]
+            ixvecs = piv["ixvecs_final"][...]
+            iyvecs = piv["iyvecs_final"][...]
+            deltaxs = piv["deltaxs_final"][...]
+            deltays = piv["deltays_final"][...]
+
+    else:
+        raise NotImplementedError
+
+    return deltaxs, deltays, ixvecs, iyvecs
+
+
+class VectorFieldsViewer(AppMatplotlibWidgets):
+    """A simple vector field viewer."""
+
+    @classmethod
+    def parse_args(cls):
+
+        parser = argparse.ArgumentParser(
+            description=cls.__doc__,
+            formatter_class=argparse.RawDescriptionHelpFormatter,
+        )
+        parser.add_argument(
+            "path",
+            help="Path file or directory.",
+            type=str,
+            nargs="?",
+            default=os.getcwd(),
+        )
+        parser.add_argument(
+            "-v", "--verbose", help="verbose mode", action="count"
+        )
+
+        return parser.parse_args()
+
+    def __init__(self, args):
+        super().__init__()
+
+        path = Path(args.path).absolute()
+
+        if path.is_file():
+            path_file_init = path
+        else:
+            path_file_init = None
+
+        if path.is_dir():
+            try:
+                path = next(path.glob("piv*"))
+            except StopIteration:
+                print(f"No PIV files found in {args.path}")
+                sys.exit(1)
+
+        serie = self.serie = SerieOfArraysFromFiles(path)
+
+        if not serie:
+            print(f"Not PIV file found (from {args.path=})")
+            sys.exit(1)
+
+        self.path_dir = Path(serie.path_dir)
+
+        # initialize the figure
+        fig = self.fig = plt.figure()
+        self.ax = fig.add_axes([0.07, 0.15, 0.9, 0.78])
+
+        self._init_name_files()
+
+        if path_file_init is None:
+            path_file_init = self.path_dir / self.name_files[0]
+            self.index_file = 0
+        else:
+            self.index_file = self.name_files.index(path_file_init.name)
+
+        self._init_figure(path_file_init)
+
+        plt.show()
+
+    def _init_name_files(self):
+
+        self.name_files = sorted(
+            p.name
+            for p in self.path_dir.glob(
+                self.serie.base_name + "*" + self.serie.extension_file
+            )
+        )
+        self.num_files = len(self.name_files)
+        self.fig.canvas.manager.set_window_title(
+            f"{self.num_files} PIV files in {self.path_dir}"
+        )
+
+    def _init_figure(self, path_file_init):
+
+        self.ax.set_title(path_file_init.name)
+
+        deltaxs, deltays, ixvecs, iyvecs = get_piv_data_from_path(path_file_init)
+
+        self.ax.invert_yaxis()
+
+        self._quiver = self.ax.quiver(
+            ixvecs, iyvecs, deltaxs, deltays, angles="xy", scale_units="xy"
+        )
+
+        y = size_button / 3.0
+
+        self._create_text_box(
+            self.fig,
+            [0.1, y, size_button, size_button],
+            "index = ",
+            self._change_index_from_textbox,
+            str(self.index_file),
+        )
+
+        function_buttons = [self._decrement_index, self._increment_index]
+        for x, name, func in zip(x_buttons, name_buttons, function_buttons):
+            self._create_button(
+                self.fig, [x, y, size_button, size_button], name, func
+            )
+
+    def _increment_index(self, event=None):
+        self._set_index(self.index_file + 1)
+
+    def _decrement_index(self, event=None):
+        self._set_index(self.index_file - 1)
+
+    def _change_index_from_textbox(self, text):
+        try:
+            index = int(text)
+        except ValueError:
+            self._set_textbox_value(self.index_file)
+            return
+        if index >= self.num_files:
+            index = self.num_files - 1
+        elif index < 0:
+            index = 0
+        self._set_textbox_value(index)
+        self._set_index(index)
+
+    def _set_textbox_value(self, value):
+        textbox = self.get_textbox("index = ")
+        textbox.set_val(str(value))
+
+    def _set_index(self, index):
+        if index == self.index_file:
+            return
+        self.index_file = index % self.num_files
+        self._set_textbox_value(self.index_file)
+        self._update_fig()
+
+    def _update_fig(self):
+        path_file = self.path_dir / self.name_files[self.index_file]
+        deltaxs, deltays, ixvecs, iyvecs = get_piv_data_from_path(path_file)
+        self.ax.set_title(path_file.name)
+        self._quiver.set_UVC(deltaxs, deltays)
+
+
+def main():
+    args = VectorFieldsViewer.parse_args()
+    return VectorFieldsViewer(args)
diff --git a/src/fluidimage/gui/test_piv_viewer.py b/src/fluidimage/gui/test_piv_viewer.py
new file mode 100644
index 00000000..e38d92a6
--- /dev/null
+++ b/src/fluidimage/gui/test_piv_viewer.py
@@ -0,0 +1,40 @@
+import sys
+
+from fluidimage import get_path_image_samples
+from fluidimage.gui.piv_viewer import main
+
+
+def test_main(monkeypatch):
+
+    path_image_samples = get_path_image_samples()
+    path = path_image_samples / "Milestone"
+
+    command = f"fluidpivviewer {path}"
+
+    with monkeypatch.context() as ctx:
+        ctx.setattr(sys, "argv", command.split())
+        viewer = main()
+
+    assert viewer.index_file == 0
+
+    path = path / "piv_0000a-b.h5"
+    command = f"fluidpivviewer {path}"
+
+    with monkeypatch.context() as ctx:
+        ctx.setattr(sys, "argv", command.split())
+        viewer = main()
+
+    assert viewer.index_file == 0
+
+    viewer._increment_index()
+    assert viewer.index_file == 1
+
+    viewer._change_index_from_textbox("10")
+    assert viewer.index_file == 1
+
+    viewer._change_index_from_textbox("-1")
+    assert viewer.index_file == 0
+
+    viewer._decrement_index()
+
+    viewer._change_index_from_textbox("abc")
diff --git a/src/fluidimage/meson.build b/src/fluidimage/meson.build
index bb05b337..284b2ba8 100644
--- a/src/fluidimage/meson.build
+++ b/src/fluidimage/meson.build
@@ -9,6 +9,7 @@ python_sources = [
   'image2image.py',
   'optical_flow.py',
   'piv.py',
+  'preproc.py',
   'run_from_xml.py',
   'synthetic.py',
   'test_image2image.py',
@@ -26,7 +27,6 @@ subdir('data_objects')
 subdir('executors')
 subdir('gui')
 subdir('postproc')
-subdir('preproc')
 subdir('reconstruct')
 subdir('topologies')
 subdir('util')
diff --git a/src/fluidimage/preproc/__init__.py b/src/fluidimage/preproc.py
similarity index 86%
rename from src/fluidimage/preproc/__init__.py
rename to src/fluidimage/preproc.py
index 9c1cd08f..009fb087 100644
--- a/src/fluidimage/preproc/__init__.py
+++ b/src/fluidimage/preproc.py
@@ -5,16 +5,6 @@
 undesirable effects. Preprocessing images by careful use of thresholds and
 filters can significantly improve the quality of PIV.
 
-Provides:
-
-.. autosummary::
-   :toctree:
-
-   toolbox
-   _toolbox_cv
-   _toolbox_py
-   io
-
 Provides
 
 .. autoclass:: Work
diff --git a/src/fluidimage/topologies/preproc.py b/src/fluidimage/topologies/preproc.py
index e123179a..d6080456 100644
--- a/src/fluidimage/topologies/preproc.py
+++ b/src/fluidimage/topologies/preproc.py
@@ -18,7 +18,7 @@
 from fluidimage.data_objects.preproc import PreprocResults, get_name_preproc
 from fluidimage.topologies import TopologyBaseFromSeries, prepare_path_dir_result
 from fluidimage.topologies.splitters import SplitterFromSeries
-from fluidimage.util import imread, logger
+from fluidimage.util import imread
 from fluidimage.works import image2image
 from fluidimage.works.preproc import (
     WorkPreproc,
diff --git a/src/fluidimage/works/meson.build b/src/fluidimage/works/meson.build
index 1c68c7b9..49666c92 100644
--- a/src/fluidimage/works/meson.build
+++ b/src/fluidimage/works/meson.build
@@ -4,7 +4,6 @@ python_sources = [
   'bos.py',
   'image2image.py',
   'optical_flow.py',
-  'preproc.py',
   'surface_tracking.py',
   'with_mask.py',
   'test_bos.py',
@@ -18,3 +17,4 @@ py.install_sources(
 )
 
 subdir('piv')
+subdir('preproc')
diff --git a/src/fluidimage/works/preproc.py b/src/fluidimage/works/preproc/__init__.py
similarity index 94%
rename from src/fluidimage/works/preproc.py
rename to src/fluidimage/works/preproc/__init__.py
index 4c2c4a7f..d474640e 100644
--- a/src/fluidimage/works/preproc.py
+++ b/src/fluidimage/works/preproc/__init__.py
@@ -5,6 +5,16 @@
 
 Provides:
 
+.. autosummary::
+   :toctree:
+
+   toolbox
+   _toolbox_cv
+   _toolbox_py
+   io
+
+Provides:
+
 .. autoclass:: WorkPreproc
    :members:
    :private-members:
@@ -24,8 +34,7 @@
     get_ind_middle,
 )
 from fluidimage.util import print_memory_usage
-
-from . import BaseWorkFromSerie
+from fluidimage.works import BaseWorkFromSerie
 
 
 def _make_doc_with_filtered_params_doc(cls):
@@ -40,11 +49,11 @@ def _make_doc_with_filtered_params_doc(cls):
 
 def _get_backend_class(backend):
     if backend == "python":
-        from fluidimage.preproc.toolbox import PreprocToolsPy
+        from fluidimage.works.preproc.toolbox import PreprocToolsPy
 
         return PreprocToolsPy
     elif backend == "opencv":
-        from fluidimage.preproc.toolbox import PreprocToolsCV
+        from fluidimage.works.preproc.toolbox import PreprocToolsCV
 
         return PreprocToolsCV
 
diff --git a/src/fluidimage/preproc/_toolbox_cv.py b/src/fluidimage/works/preproc/_toolbox_cv.py
similarity index 99%
rename from src/fluidimage/preproc/_toolbox_cv.py
rename to src/fluidimage/works/preproc/_toolbox_cv.py
index 65406a56..d7fa7cd0 100644
--- a/src/fluidimage/preproc/_toolbox_cv.py
+++ b/src/fluidimage/works/preproc/_toolbox_cv.py
@@ -12,7 +12,8 @@
 
 import numpy as np
 
-from .._opencv import cv2
+from fluidimage._opencv import cv2
+
 from .io import iterate_multiple_imgs
 
 __all__ = [
diff --git a/src/fluidimage/preproc/_toolbox_py.py b/src/fluidimage/works/preproc/_toolbox_py.py
similarity index 100%
rename from src/fluidimage/preproc/_toolbox_py.py
rename to src/fluidimage/works/preproc/_toolbox_py.py
diff --git a/src/fluidimage/preproc/io.py b/src/fluidimage/works/preproc/io.py
similarity index 100%
rename from src/fluidimage/preproc/io.py
rename to src/fluidimage/works/preproc/io.py
diff --git a/src/fluidimage/preproc/meson.build b/src/fluidimage/works/preproc/meson.build
similarity index 79%
rename from src/fluidimage/preproc/meson.build
rename to src/fluidimage/works/preproc/meson.build
index 557923ca..d1861c78 100644
--- a/src/fluidimage/preproc/meson.build
+++ b/src/fluidimage/works/preproc/meson.build
@@ -9,5 +9,5 @@ python_sources = [
 
 py.install_sources(
   python_sources,
-  subdir: 'fluidimage/preproc'
+  subdir: 'fluidimage/works/preproc'
 )
diff --git a/src/fluidimage/preproc/toolbox.py b/src/fluidimage/works/preproc/toolbox.py
similarity index 99%
rename from src/fluidimage/preproc/toolbox.py
rename to src/fluidimage/works/preproc/toolbox.py
index 946b6313..93c5e991 100644
--- a/src/fluidimage/preproc/toolbox.py
+++ b/src/fluidimage/works/preproc/toolbox.py
@@ -20,8 +20,7 @@
 import inspect
 
 from fluidimage._opencv import error_import_cv2
-
-from ..util import logger
+from fluidimage.util import logger
 
 
 class PreprocToolsBase: