@@ -75,8 +75,8 @@ New features
     False
 
 * allowed arrays to have metadata (e.g. title, description, authors, ...).
-  Metadata can be accessed using the syntax ``array.meta.name``.
-  See bellow for use cases:
+  Array metadata can be accessed using the syntax ``array.meta.name``.
+  See below for use cases:
 
     >>> # add metadata to/from an array
     >>> # for Python <= 3.5
@@ -93,8 +93,8 @@ New features
 
   Warnings:
 
-  - Currently, only the HDF (.h5) file format supports saving and loading metadata.
-  - Metadata are not kept when actions or methods are applied on a array
+  - Currently, only the HDF (.h5) file format supports saving and loading array metadata.
+  - Metadata is not kept when actions or methods are applied on an array
     except for operations modifying the object in-place, such as `pop[age < 10] = 0`,
     and when the method `copy()` is called. Do not add metadata to an array if you know
     you will apply actions or methods on it before dumping it.
@@ -127,6 +127,32 @@ New features
     3.141592653589793
 
 
+* allowed sessions to have metadata.
+  Like for arrays, session metadata can be accessed using the syntax ``session.meta.name``.
+  See below for use cases:
+
+    >>> # add metadata to a session at creation
+    >>> # Python <= 3.5
+    >>> s = Session([('arr1', ndtest(2)), ('arr2', ndtest(3)], meta=[('title', 'my title'), ('author', 'John Smith')])
+    >>> # Python 3.6+
+    >>> s = Session(arr1=ndtest(2), arr2=ndtest(3), meta=Metadata(title='my title', author='John Smith'))
+    >>> # show/access metadata
+    >>> s.meta
+    title: my title
+    author: John Smith
+
+  Warnings:
+
+  - Contrary to array metadata, saving and loading session metadata is supported for
+    all current session file formats: Excel, CSV and HDF (.h5)
+  - Metadata is not kept when actions or methods are applied on a session
+    except for operations modifying a specific array, such as: `s['arr1'] = 0`.
+    Do not add metadata to a session if you know you will apply actions or methods
+    on it before dumping it.
+
+  Closes :issue:`640`.
+
+
 .. _misc:
 
 Miscellaneous improvements
 
@@ -687,7 +687,7 @@ class LArray(ABCLArray):
 
     Warnings
     --------
-    Metadata are not kept when actions or methods are applied on a array
+    Metadata is not kept when actions or methods are applied on an array
     except for operations modifying the object in-place, such as: `pop[age < 10] = 0`.
     Do not add metadata to an array if you know you will apply actions or methods
     on it before dumping it.
@@ -8097,7 +8097,7 @@ def eye(rows, columns=None, k=0, title=None, dtype=None, meta=None):
 #       ('FR', 'M'): 2, ('FR', 'F'): 3,
 #       ('DE', 'M'): 4, ('DE', 'F'): 5})
 
-# TODO: add metadata to returned Session once Session will handle metadata
+
 def stack(elements=None, axis=None, title=None, meta=None, **kwargs):
     """
     Combines several arrays or sessions along an axis.
@@ -8285,7 +8285,7 @@ def stack(elements=None, axis=None, title=None, meta=None, **kwargs):
             except Exception:
                 stacked = nan
             res.append((name, stacked))
-        return Session(res)
+        return Session(res, meta=meta)
     else:
         # XXX : use concat?
         result_axes = AxisCollection.union(*[get_axes(v) for v in values])
 
@@ -2,7 +2,7 @@
 from __future__ import absolute_import, division, print_function
 
 from collections import OrderedDict
-from larray.util.misc import PY2
+from larray.util.misc import PY2, basestring
 
 
 __all__ = ['Metadata']
@@ -31,6 +31,13 @@ def __delattr__(self, key):
             od = object.__getattribute__(self, '__odict')
             del od[key]
 
+        def __reduce__(self):
+            'Return state information for pickling'
+            od = object.__getattribute__(self, '__odict')
+            res = list(od.__reduce__())
+            res[0] = self.__class__
+            return tuple(res)
+
         def __dir__(self):
             od = object.__getattribute__(self, '__odict')
             return list(set(dir(self.__class__)) | set(self.__dict__.keys()) | set(od.keys()))
@@ -56,9 +63,6 @@ def method(self, *args, **kwargs):
         __iter__ = method_factory('iter')
         __len__ = method_factory('len')
 
-        __reduce__ = method_factory('reduce')
-        __reduce_ex__ = method_factory('reduce_ex')
-
         __reversed__ = method_factory('reversed')
 
         __sizeof__ = method_factory('sizeof')
@@ -143,6 +147,29 @@ class Metadata(AttributeDict):
     >>> del arr.meta.creation_date
     """
 
+    # TODO: use LArray.from_dict once ready (issue 581)
+    def __larray__(self):
+        from larray.core.array import LArray
+        from larray.core.axis import Axis
+        return LArray(list(self.values()), Axis(self.keys(), name='metadata'))
+
+    @classmethod
+    def from_array(cls, array):
+        from larray.core.array import aslarray
+        array = aslarray(array)
+        if array.ndim != 1:
+            raise ValueError("Expected LArray object of dimension 1. Got array of dimension {}".format(array.ndim))
+
+        from pandas import to_numeric, to_datetime
+
+        def _convert_value(value):
+            value = to_numeric([value], errors='ignore')[0]
+            if isinstance(value, basestring):
+                value = to_datetime(value, errors='ignore', infer_datetime_format=True)
+            return value
+
+        return Metadata([(key, _convert_value(value)) for key, value in zip(array.axes.labels[0], array.data)])
+
     # ---------- IO methods ----------
     def to_hdf(self, hdfstore, key):
         if len(self):