diff --git a/R/loom_utils.R b/R/loom_utils.R
new file mode 100755
index 0000000..88f4990
--- /dev/null
+++ b/R/loom_utils.R
@@ -0,0 +1,353 @@
+#!/usr/bin/env Rscript
+
+exchangeable_loom_version <- '3.0.0alpha'
+
+isExchangeableLoom <- function(h5f) {
+    attrs <- h5readAttributes(h5f, '/')
+    version <- attrs[['LOOM_SPEC_VERSION']]
+    return(!is.null(version) && version == exchangeable_loom_version)
+}
+
+readDimNames <- function(h5f) {
+    cell_attr <- h5readAttributes(h5f, '/col_attrs')[['CellID']]
+    gene_attr <- h5readAttributes(h5f, '/row_attrs')[['Gene']]
+    source <- h5readAttributes(h5f, '/')[['created_from']]
+    if (!is.null(source) && source == 'anndata') {
+        if (is.null(cell_attr))
+            cell_attr <- 'obs_names'
+        if (is.null(gene_attr))
+            gene_attr <- 'var_names'
+    }
+    return(list(col=cell_attr, row=gene_attr))
+}
+
+readManifest <- function(h5f) {
+    tryCatch({
+        manifest <- data.frame(t(h5read(h5f, '/global/manifest')), stringsAsFactors=FALSE)
+        colnames(manifest) <- c('loom_path', 'dtype', 'anndata_path', 'sce_path')
+        return(manifest)
+    },
+    error=function(e) {
+        manifest <- NULL
+        return(manifest)
+    })
+}
+
+nestedEnvAsList <- function(x) {
+    out <- as.list(x)
+    lapply(out, function(e) if (is.environment(e)) nestedEnvAsList(e) else e)
+}
+
+nestedEnv <- function(root_env, paths, v) {
+    n <- length(paths)
+    var <- paths[1]
+    if (n == 1) {
+        root_env[[var]] <- v
+    } else {
+        if (is.null(root_env[[var]]))
+            root_env[[var]] <- new.env(parent=emptyenv())
+        nestedEnv(root_env[[var]], paths[2:n], v)
+    }
+    invisible()
+}
+
+flattenNestedListToEnv <- function(x, e, prefix=NULL) {
+    entry_names <- names(x)
+    if (is.null(entry_names)) entry_names <- seq(length(x))
+    sapply(entry_names, function(name) {
+        if (is.null(prefix)) {
+            full_name <- name
+        } else {
+            full_name <- paste(prefix, name, sep='__')
+        }
+        if (is.list(x[[name]])) {
+            flattenNestedListToEnv(x[[name]], e, full_name)
+        } else {
+            e[[full_name]] <- x[[name]]
+        }
+    })
+    invisible()
+}
+
+makeManifest <- function(entries, dtype='array', loom_prefix='/global/', anndata_prefix='/uns/',
+                         sce_prefix='@metadata$') {
+    n <- length(entries)
+    if (is.list(entries)) {
+        entry_names <- names(entries)
+        is_scalar <- sapply(entries, function(x) is.vector(x) && length(x) == 1)
+        dtypes <- ifelse(is_scalar, 'scalar', 'array')
+    } else {
+        entry_names <- entries
+        dtypes <- rep(dtype, n)
+    }
+    loom_paths <- paste0(loom_prefix, entry_names)
+    if (endsWith(loom_prefix, '['))
+        loom_paths <- paste0(loom_paths, ']')
+    if (is.null(anndata_prefix)) {
+        anndata_paths <- rep('', n)
+    } else {
+        if (anndata_prefix == '/obsm/X_') {
+            ad_names <- tolower(entry_names)
+        } else {
+            ad_names <- gsub('__', '/', entry_names)
+        }
+        anndata_paths <- paste0(anndata_prefix, ad_names)
+    }
+    if (startsWith(sce_prefix, '@metadata$'))
+        entry_names <- gsub('__', '$', entry_names)
+    sce_paths <- paste0(sce_prefix, entry_names)
+    return(data.frame(loom_path=loom_paths, dtype=dtypes, anndata_path=anndata_paths,
+                      sce_path=sce_paths, stringsAsFactors=FALSE))
+}
+
+readExchangeableLoom <- function(filename, backed=TRUE) {
+    stopifnot(file.exists(filename), H5Fis_hdf5(filename))
+    h5f <- H5Fopen(filename, flag='H5F_ACC_RDONLY')
+    if (!isExchangeableLoom(h5f)) {
+        H5Fclose(h5f)
+        return(LoomExperiment::import(filename, type='SingleCellLoomExperiment'))
+    }
+    dim_names <- readDimNames(h5f)
+    manifest <- readManifest(h5f)
+    h5closeAll()
+
+    suppressWarnings(scle <- LoomExperiment::import(
+            filename,
+            type='SingleCellLoomExperiment',
+            rownames_attr=dim_names$row,
+            colnames_attr=dim_names$col))
+    if (!backed) {
+        for (i in seq_along(assays(scle))) {
+            assays(scle)[[i]] <- as(assays(scle)[[i]], 'dgCMatrix')
+        }
+    }
+
+    h5f <- H5Fopen(filename, flag='H5F_ACC_RDONLY')
+
+    # Add appropriate assay name
+    mx_attrs <- h5readAttributes(h5f, '/matrix')
+    if ('assay' %in% names(mx_attrs)) {
+        names(assays(scle))[1] <- mx_attrs['assay']
+    } else {
+        names(assays(scle))[1] <- 'counts'
+    }
+
+    if (!is.null(manifest)) {
+
+        # Graphs are already handled by import(), just record entries
+        is_graph <- (startsWith(manifest$loom_path, '/col_graphs/') |
+                    startsWith(manifest$loom_path, '/row_graphs/'))
+
+        # Handle reducedDims
+        is_rd <- startsWith(manifest$loom_path, '/global/reducedDims__')
+        rd_paths <- manifest$loom_path[is_rd]
+        names(rd_paths) <- sub('^@reducedDims@listData[$]', '', manifest$sce_path[is_rd])
+        reducedDims(scle) <- SimpleList(lapply(rd_paths, function(path) {
+            mat <- t(h5read(h5f, path))
+            rownames(mat) <- colnames(scle)
+            mat
+        }))
+
+        # Handle global attributes
+        is_attr <- startsWith(manifest$loom_path, '/.attrs[')
+        src_paths <- manifest$loom_path[is_attr]
+        tgt_paths <- manifest$sce_path[is_attr]
+        attr_names <- substr(src_paths, 9, nchar(src_paths)-1)
+        global_attrs <- h5readAttributes(h5f, '/')
+        mtdt <- new.env(parent=emptyenv(), size=length(tgt_paths))
+        for (i in seq_along(attr_names)) {
+            v <- global_attrs[[ attr_names[i] ]]
+            paths <- unlist(strsplit(sub('^@metadata[$]', '', tgt_paths[i]), '$', fixed=TRUE))
+            nestedEnv(mtdt, paths, v)
+            scle@metadata[[ attr_names[i] ]] <- NULL
+        }
+
+        # Handle global datasets
+        is_ds <- (!(is_graph | is_rd | is_attr) & manifest$sce_path != '')
+        src_paths <- manifest$loom_path[is_ds]
+        tgt_paths <- manifest$sce_path[is_ds]
+        for (i in seq_along(tgt_paths)) {
+            v <- h5read(h5f, src_paths[i])
+            paths <- unlist(strsplit(sub('^@metadata[$]', '', tgt_paths[i]), '$', fixed=TRUE))
+            nestedEnv(mtdt, paths, v)
+        }
+        mtdt <- nestedEnvAsList(mtdt)
+        for (name in names(mtdt)) {
+            scle@metadata[[name]] <- mtdt[[name]]
+        }
+    }
+    h5closeAll()
+
+    return(as(scle, 'SingleCellExperiment'))
+}
+
+writeExchangeableLoom <- function(sce, filename, main_layer=NULL, return_manifest=FALSE) {
+    scle <- LoomExperiment::SingleCellLoomExperiment(sce)
+
+    # Clean rowData and colData
+    row_fct_idx <- sapply(rowData(scle), is.factor)
+    rowData(scle)[row_fct_idx] <- lapply(
+        rowData(scle)[row_fct_idx], function(x) type.convert(as.character(x), as.is=TRUE))
+    col_fct_idx <- sapply(colData(scle), is.factor)
+    colData(scle)[col_fct_idx] <- lapply(
+        colData(scle)[col_fct_idx], function(x) type.convert(as.character(x), as.is=TRUE))
+
+    # Handle reducedDims. Move embeddings out of reducedDims so they don't get
+    # written to unwanted location by export().
+    rdims <- reducedDims(scle)
+    reducedDims(scle) <- SimpleList()
+    if (!isEmpty(rdims)) {
+        rdim_manifest <- makeManifest(
+            names(rdims),
+            dtype='array',
+            loom_prefix='/global/reducedDims__',
+            anndata_prefix='/obsm/X_',
+            sce_prefix='@reducedDims@listData$')
+    } else {
+        rdim_manifest <- NULL
+    }
+
+    # Handle graphs. They get written by export() but we still need to record the paths.
+    if (!isEmpty(colGraphs(scle))) {
+        colgraph_manifest <- makeManifest(
+            names(colGraphs(scle)),
+            dtype='graph',
+            loom_prefix='/col_graphs/',
+            anndata_prefix='/uns/',
+            sce_prefix='@colGraphs$')
+    } else {
+        colgraph_manifest <- NULL
+    }
+    if (!isEmpty(rowGraphs(scle))) {
+        rowgraph_manifest <- makeManifest(
+            names(rowGraphs(scle)),
+            dtype='graph',
+            loom_prefix='/row_graphs/',
+            anndata_prefix=NULL,
+            sce_prefix='@rowGraphs$')
+    } else {
+        rowgraph_manifest <- NULL
+    }
+
+    # Handle metadata. Flatten nested lists to make export() happy. Scalars go
+    # to /.attrs, others go to /global
+    if (length(metadata(scle)) > 0) {
+        mtdt <- new.env(parent=emptyenv())
+        flattenNestedListToEnv(scle@metadata, mtdt)
+        mtdt <- lapply(mtdt, function(x) {
+            if (!is.numeric(x) && !is.character(x) && !is.logical(x))
+                x <- type.convert(as.character(x), as.is=TRUE)
+            if ('class' %in% names(attributes(x)))
+                attributes(x)$class <- NULL
+            x
+        })
+        is_attr <- rep(FALSE, length(mtdt))
+        names(is_attr) <- names(mtdt)
+        for (i in seq_along(mtdt)) {
+            x <- mtdt[[i]]
+            if ((is.vector(x) || is.array(x)) && (length(x) == 1)) {
+                is_attr[i] <- TRUE
+                mtdt[[i]] <- x[1]
+            }
+        }
+        is_attr <- is_attr & !grepl('__', names(mtdt))
+
+        # Let export handle attributes
+        metadata(scle) <- mtdt[is_attr]
+
+        excluded_from_manifest <- c('LOOM_SPEC_VERSION', 'CreationDate', 'last_modified',
+                            'CreatedWith', 'LoomExperiment-class', 'created_from',
+                            'last_modified_by')
+        attr_names <- names(metadata(scle))
+        attr_names <- attr_names[!attr_names %in% excluded_from_manifest]
+        if (length(attr_names) > 0) {
+            attr_manifest <- makeManifest(
+                attr_names,
+                dtype='scalar',
+                loom_prefix='/.attrs[',
+                anndata_prefix='/uns/',
+                sce_prefix='@metadata$')
+        } else {
+            attr_manifest <- NULL
+        }
+
+        datasets <- mtdt[!is_attr]
+        if (length(datasets) > 0) {
+            dts_manifest <- makeManifest(
+                datasets,
+                dtype=NULL,
+                loom_prefix='/global/',
+                anndata_prefix='/uns/',
+                sce_prefix='@metadata$')
+        } else {
+            dts_manifest <- NULL
+        }
+    } else {
+        attr_manifest <- NULL
+        dts_manifest <- NULL
+        datasets <- list()
+    }
+
+    manifest <- rbind(attr_manifest, dts_manifest, rdim_manifest, colgraph_manifest, rowgraph_manifest)
+
+    # Write to loom by LoomExperiment::export
+    if (file.exists(filename))
+        file.remove(filename)
+    suppressWarnings(export(
+        scle,
+        filename,
+        matrix=ifelse(!is.null(main_layer) && main_layer %in% assayNames(scle),
+                      main_layer, assayNames(scle)[1]),
+        colnames_attr='obs_names',
+        rownames_attr='var_names'))
+    h5closeAll()
+
+    # Write extra bits
+    h5f <- H5Fopen(filename)
+
+    # Write extra global attributes
+    h5writeAttribute(exchangeable_loom_version, h5f, 'LOOM_SPEC_VERSION')
+    h5writeAttribute('sce', h5f, 'created_from')
+
+    # Write column names of 'CellID' and 'Gene' as attributes of '/col_attrs' and '/row_attrs'
+    h5g_ca <- H5Gopen(h5f, '/col_attrs')
+    h5writeAttribute('obs_names', h5g_ca, 'CellID')
+    h5g_ra <- H5Gopen(h5f, '/row_attrs')
+    h5writeAttribute('var_names', h5g_ra, 'Gene')
+
+    # Write primary asssay name as attribute of '/matrix'
+    h5d_mx <- H5Dopen(h5f, '/matrix')
+    h5writeAttribute('assay', h5d_mx, names(assays(scle))[1])
+
+    # Write manifest
+    h5createGroup(h5f, '/global')
+    if (!is.null(manifest)) {
+        manifest <- manifest[order(manifest$dtype, manifest$loom_path), ]
+        h5write(t(manifest), h5f, '/global/manifest')
+    }
+
+    # Write reducedDims
+    for (i in seq_along(rdims)) {
+        rdim <- rdims[[i]]
+        loom_path <- rdim_manifest$loom_path[i]
+        h5write(t(rdim), h5f, loom_path)
+    }
+
+    # Write extra global datasets
+    for (i in seq_along(datasets)) {
+        dts <- datasets[[i]]
+        loom_path <- dts_manifest$loom_path[i]
+        h5write(dts, h5f, loom_path)
+    }
+
+    # Remove '/col_attrs/reducedDims' to make anndata happy
+    h5delete(h5f, '/col_attrs/reducedDims')
+    h5closeAll()
+
+    if (return_manifest) {
+        return(manifest)
+    } else {
+        invisible()
+    }
+}
+