diff --git a/docs/source/erlab.accessors.rst b/docs/source/erlab.accessors.rst
index 29f5eebe..22aaf2eb 100644
--- a/docs/source/erlab.accessors.rst
+++ b/docs/source/erlab.accessors.rst
@@ -1,14 +1,4 @@
-Extensions to xarray (:mod:`erlab.accessors`)
-=============================================
+Accessors (:mod:`erlab.accessors`)
+==================================
 
 .. automodule:: erlab.accessors
-
-
-   .. rubric:: Classes
-
-   .. autosummary::
-
-      PlotAccessor
-      ImageToolAccessor
-      SelectionAccessor
-      MomentumAccessor
diff --git a/docs/source/erlab.characterization.rst b/docs/source/erlab.characterization.rst
deleted file mode 100644
index b3fc0eb6..00000000
--- a/docs/source/erlab.characterization.rst
+++ /dev/null
@@ -1,4 +0,0 @@
-Characterization (:mod:`erlab.characterization`)
-================================================
-
-.. automodule:: erlab.characterization
diff --git a/docs/source/reference.rst b/docs/source/reference.rst
index 8decc1ab..eacba377 100644
--- a/docs/source/reference.rst
+++ b/docs/source/reference.rst
@@ -2,7 +2,7 @@
 API Reference
 *************
 
-ERLabPy is organized into multiple subpackages and submodules.
+ERLabPy is organized into multiple subpackages and submodules classified by their functionality. The following table lists the subpackages and submodules of ERLabPy.
 
 Subpackages
 ===========
@@ -10,11 +10,11 @@ Subpackages
 ========================   ========================
 Subpackage                 Description
 ========================   ========================
-`erlab.analysis`           Data analysis
-`erlab.io`                 Read & write ARPES data
-`erlab.plotting`           Plot
-`erlab.interactive`        Interactive plotting based on Qt and pyqtgraph
-`erlab.characterization`   Analyze sample characterization results such as XRD and transport measurements
+`erlab.analysis`           Routines for analyzing ARPES data.
+`erlab.io`                 Reading and writing data.
+`erlab.plotting`           Functions related to static plotting with matplotlib.
+`erlab.interactive`        Interactive tools and widgets based on Qt and pyqtgraph
+`erlab.accessors`          `xarray accessors <https://docs.xarray.dev/en/stable/internals/extending-xarray.html>`_. You will not need to import this module directly.
 ========================   ========================
 
 .. currentmodule:: erlab
@@ -26,7 +26,7 @@ Subpackage                 Description
    erlab.io
    erlab.plotting
    erlab.interactive
-   erlab.characterization
+   erlab.accessors
 
 Submodules
 ==========
@@ -35,9 +35,8 @@ Submodules
 Submodule           Description
 ==================  ==================
 `erlab.lattice`     Tools for working with real and reciprocal lattices.
-`erlab.constants`   Physical constants and unit conversion
-`erlab.accessors`   `xarray accessors <https://docs.xarray.dev/en/stable/internals/extending-xarray.html>`_
-`erlab.parallel`    Helpers for parallel processing
+`erlab.constants`   Physical constants and functions for unit conversion.
+`erlab.parallel`    Helpers for parallel processing.
 ==================  ==================
 
 .. toctree::
@@ -45,5 +44,4 @@ Submodule           Description
 
    erlab.lattice
    erlab.constants
-   erlab.accessors
    erlab.parallel
diff --git a/src/erlab/characterization/__init__.py b/src/erlab/characterization/__init__.py
index aab49998..cbf7ee98 100644
--- a/src/erlab/characterization/__init__.py
+++ b/src/erlab/characterization/__init__.py
@@ -1,15 +1,8 @@
-"""
-Data import and analysis for characterization experiments.
-
-.. currentmodule:: erlab.characterization
-
-Modules
-=======
-
-.. autosummary::
-   :toctree: generated
-
-   xrd
-   resistance
-
-"""
+import warnings
+from erlab.io.characterization import xrd, resistance  # noqa: F401
+
+warnings.warn(
+    "`erlab.characterization` is deprecated. Use `erlab.io.characterization` instead",
+    DeprecationWarning,
+    stacklevel=2,
+)
diff --git a/src/erlab/io/__init__.py b/src/erlab/io/__init__.py
index 0cd82616..41d7177f 100644
--- a/src/erlab/io/__init__.py
+++ b/src/erlab/io/__init__.py
@@ -16,6 +16,7 @@
    utilities
    igor
    exampledata
+   characterization
 
 
 For a single session, it is very common to use only one type of loader for a single
diff --git a/src/erlab/io/characterization/__init__.py b/src/erlab/io/characterization/__init__.py
new file mode 100644
index 00000000..b8ec9f36
--- /dev/null
+++ b/src/erlab/io/characterization/__init__.py
@@ -0,0 +1,14 @@
+"""Data import for characterization experiments.
+
+.. currentmodule:: erlab.io.characterization
+
+Modules
+=======
+
+.. autosummary::
+   :toctree:
+
+   xrd
+   resistance
+
+"""
diff --git a/src/erlab/characterization/resistance.py b/src/erlab/io/characterization/resistance.py
similarity index 97%
rename from src/erlab/characterization/resistance.py
rename to src/erlab/io/characterization/resistance.py
index 427ddb06..69fdb543 100644
--- a/src/erlab/characterization/resistance.py
+++ b/src/erlab/io/characterization/resistance.py
@@ -1,4 +1,4 @@
-"""Functions related to analyzing temperature-dependent resistance data.
+"""Functions related to loading temperature-dependent resistance data.
 
 Currently only supports loading raw data from ``.dat`` and ``.csv`` files output by
 physics lab III equipment.
diff --git a/src/erlab/characterization/xrd.py b/src/erlab/io/characterization/xrd.py
similarity index 96%
rename from src/erlab/characterization/xrd.py
rename to src/erlab/io/characterization/xrd.py
index 46450bc0..a142f38d 100644
--- a/src/erlab/characterization/xrd.py
+++ b/src/erlab/io/characterization/xrd.py
@@ -1,4 +1,4 @@
-"""Functions related to analyzing x-ray diffraction spectra.
+"""Functions related to loading x-ray diffraction spectra.
 
 Currently only supports loading raw data from igor ``.itx`` files.