diff --git a/docs/source/_rst/code.rst b/docs/source/_rst/code.rst
new file mode 100644
index 0000000..0916b80
--- /dev/null
+++ b/docs/source/_rst/code.rst
@@ -0,0 +1,7 @@
+Code Documentation
+==================
+
+.. toctree::
+    :maxdepth: 3
+
+    LabelTensor <label_tensor.rst>
diff --git a/docs/source/_rst/label_tensor.rst b/docs/source/_rst/label_tensor.rst
new file mode 100644
index 0000000..976e839
--- /dev/null
+++ b/docs/source/_rst/label_tensor.rst
@@ -0,0 +1,12 @@
+LabelTensor
+===========
+.. currentmodule:: pina.label_tensor
+
+.. automodule:: pina.label_tensor
+
+.. autoclass:: LabelTensor
+    :members:
+    :private-members:
+    :undoc-members:
+    :show-inheritance:
+    :noindex:
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 0ca6208..b2dbc70 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -47,12 +47,14 @@ extensions = [
     'sphinx.ext.ifconfig',
     'sphinx.ext.mathjax',
 ]
+autosummary_generate = True
 
 intersphinx_mapping = {
-    'python': ('http://docs.python.org/2', None), 'numpy':
-    ('http://docs.scipy.org/doc/numpy/', None), 'scipy':
-    ('http://docs.scipy.org/doc/scipy/reference/', None), 'matplotlib':
-    ('http://matplotlib.sourceforge.net/', None)
+    'python': ('http://docs.python.org/2', None),
+    'numpy': ('http://docs.scipy.org/doc/numpy/', None),
+    'scipy': ('http://docs.scipy.org/doc/scipy/reference/', None),
+    'matplotlib': ('http://matplotlib.sourceforge.net/', None),
+    'torch': ('https://pytorch.org/docs/stable/', None)
 }
 
 # Add any paths that contain templates here, relative to this directory.
diff --git a/docs/source/index.rst b/docs/source/index.rst
index 92a64cb..d2c7b6b 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -22,6 +22,7 @@ solve problems in a continuous and nonlinear settings.
    :caption: Package Documentation:
 
    Installation <_rst/installation>
+   API <_rst/code>
    Contributing <_rst/contributing>
    License <LICENSE.rst>
 
@@ -30,7 +31,7 @@ solve problems in a continuous and nonlinear settings.
 .. ........................................................................................
 
 .. toctree::
-    :maxdepth: 2
+    :maxdepth: 1
     :numbered:
     :caption: Tutorials:
 
diff --git a/pina/label_tensor.py b/pina/label_tensor.py
index c9e219b..2b3b92c 100644
--- a/pina/label_tensor.py
+++ b/pina/label_tensor.py
@@ -1,64 +1,119 @@
+""" Module for LabelTensor """
 import torch
 
-class LabelTensor():
 
-    def __init__(self, x, labels):
-
-
-        if len(labels) != x.shape[1]:
-            print(len(labels), x.shape[1])
-            raise ValueError
-        self.__labels = labels
-        self.tensor = x
-
-    def __getitem__(self, key):
-        if isinstance(key, (tuple, list)):
-            indeces = [self.labels.index(k) for k in key]
-            return LabelTensor(self.tensor[:, indeces], [self.labels[idx] for idx in indeces])
-        if key in self.labels:
-            return self.tensor[:, self.labels.index(key)]
-        else:
-            return self.tensor.__getitem__(key)
-
-    def __repr__(self):
-        return self.tensor
-
-    def __str__(self):
-        return '{}\n {}\n'.format(self.labels, self.tensor)
-
-    @property
-    def shape(self):
-        return self.tensor.shape
-
-    @property
-    def dtype(self):
-        return self.tensor.dtype
-
-    @property
-    def device(self):
-        return self.tensor.device
-
-    @property
-    def labels(self):
-        return self.__labels
+class LabelTensor(torch.Tensor):
+    """Torch tensor with a label for any column."""
 
     @staticmethod
-    def hstack(labeltensor_list):
-        concatenated_tensor = torch.cat([lt.tensor for lt in labeltensor_list], axis=1)
-        concatenated_label = sum([lt.labels for lt in labeltensor_list], [])
-        return LabelTensor(concatenated_tensor, concatenated_label)
+    def __new__(cls, x, labels, *args, **kwargs):
+        return super().__new__(cls, x, *args, **kwargs)
 
+    def __init__(self, x, labels):
+        '''
+        Construct a `LabelTensor` by passing a tensor and a list of column
+        labels. Such labels uniquely identify the columns of the tensor,
+        allowing for an easier manipulation.
 
+        :param torch.Tensor x: the data tensor.
+        :param labels: the labels of the columns.
+        :type labels: str or iterable(str)
 
-if __name__ == "__main__":
-    import numpy as np
-    a = np.random.uniform(size=(20, 3))
-    a = np.random.uniform(size=(20, 3))
-    p = torch.from_numpy(a)
-    t = LabelTensor(p, labels=['u', 'p', 't'])
-    print(t)
-    print(t['u'])
-    t *= 2
-    print(t['u'])
-    print(t[:, 0])
+        :Example:
+            >>> from pina import LabelTensor
+            >>> tensor = LabelTensor(torch.rand((2000, 3)), ['a', 'b', 'c'])
+            >>> tensor
+            tensor([[6.7116e-02, 4.8892e-01, 8.9452e-01],
+                [9.2392e-01, 8.2065e-01, 4.1986e-04],
+                [8.9266e-01, 5.5446e-01, 6.3500e-01],
+                ...,
+                [5.8194e-01, 9.4268e-01, 4.1841e-01],
+                [1.0246e-01, 9.5179e-01, 3.7043e-02],
+                [9.6150e-01, 8.0656e-01, 8.3824e-01]])
+            >>> tensor.extract('a')
+            tensor([[0.0671],
+                    [0.9239],
+                    [0.8927],
+                    ...,
+                    [0.5819],
+                    [0.1025],
+                    [0.9615]])
+            >>> tensor.extract(['a', 'b'])
+            tensor([[0.0671, 0.4889],
+                    [0.9239, 0.8207],
+                    [0.8927, 0.5545],
+                    ...,
+                    [0.5819, 0.9427],
+                    [0.1025, 0.9518],
+                    [0.9615, 0.8066]])
+            >>> tensor.extract(['b', 'a'])
+            tensor([[0.4889, 0.0671],
+                    [0.8207, 0.9239],
+                    [0.5545, 0.8927],
+                    ...,
+                    [0.9427, 0.5819],
+                    [0.9518, 0.1025],
+                    [0.8066, 0.9615]])
+        '''
 
+        if isinstance(labels, str):
+            labels = [labels]
+
+        if len(labels) != x.shape[1]:
+            raise ValueError(
+                'the tensor has not the same number of columns of '
+                'the passed labels.'
+            )
+        self.labels = labels
+
+    def clone(self, *args, **kwargs):
+        """
+        Clone the LabelTensor. For more details, see
+        :meth:`torch.Tensor.clone`.
+
+        :return: a copy of the tensor
+        :rtype: LabelTensor
+        """
+        return LabelTensor(super().clone(*args, **kwargs), self.labels)
+
+    def to(self, *args, **kwargs):
+        """
+        Performs Tensor dtype and/or device conversion. For more details, see
+        :meth:`torch.Tensor.to`.
+        """
+        new_obj = LabelTensor([], self.labels)
+        tempTensor = super().to(*args, **kwargs)
+        new_obj.data = tempTensor.data
+        new_obj.requires_grad = tempTensor.requires_grad
+        return new_obj
+
+    def extract(self, label_to_extract):
+        """
+        Extract the subset of the original tensor by returning all the columns
+        corresponding to the passed `label_to_extract`.
+
+        :param label_to_extract: the label(s) to extract.
+        :type label_to_extract: str or iterable(str)
+        :raises TypeError: labels are not str
+        :raises ValueError: label to extract is not in the labels list
+        """
+
+        if isinstance(label_to_extract, str):
+            label_to_extract = [label_to_extract]
+        elif isinstance(label_to_extract, (tuple, list)):  # TODO
+            pass
+        else:
+            raise TypeError(
+                '`label_to_extract` should be a str, or a str iterator')
+
+        try:
+            indeces = [self.labels.index(f) for f in label_to_extract]
+        except ValueError:
+            raise ValueError('`label_to_extract` not in the labels list')
+
+        extracted_tensor = LabelTensor(
+            self[:, indeces],
+            [self.labels[idx] for idx in indeces]
+        )
+
+        return extracted_tensor
diff --git a/tests/test_label_tensor.py b/tests/test_label_tensor.py
new file mode 100644
index 0000000..dbf0d44
--- /dev/null
+++ b/tests/test_label_tensor.py
@@ -0,0 +1,61 @@
+import torch
+import pytest
+
+from pina import LabelTensor
+
+data = torch.rand((20, 3))
+labels = ['a', 'b', 'c']
+
+
+def test_constructor():
+    LabelTensor(data, labels)
+
+
+def test_wrong_constructor():
+    with pytest.raises(ValueError):
+        LabelTensor(data, ['a', 'b'])
+
+
+def test_labels():
+    tensor = LabelTensor(data, labels)
+    assert isinstance(tensor, torch.Tensor)
+    assert tensor.labels == labels
+
+
+def test_extract():
+    label_to_extract = ['a', 'c']
+    tensor = LabelTensor(data, labels)
+    new = tensor.extract(label_to_extract)
+    assert new.labels == label_to_extract
+    assert new.shape[1] == len(label_to_extract)
+    assert torch.all(torch.isclose(data[:, 0::2], new))
+
+
+def test_extract_onelabel():
+    label_to_extract = ['a']
+    tensor = LabelTensor(data, labels)
+    new = tensor.extract(label_to_extract)
+    assert new.ndim == 2
+    assert new.labels == label_to_extract
+    assert new.shape[1] == len(label_to_extract)
+    assert torch.all(torch.isclose(data[:, 0].reshape(-1, 1), new))
+
+
+def test_wrong_extract():
+    label_to_extract = ['a', 'cc']
+    tensor = LabelTensor(data, labels)
+    with pytest.raises(ValueError):
+        tensor.extract(label_to_extract)
+
+
+def test_extract_order():
+    label_to_extract = ['c', 'a']
+    tensor = LabelTensor(data, labels)
+    new = tensor.extract(label_to_extract)
+    expected = torch.cat(
+        (data[:, 2].reshape(-1, 1), data[:, 0].reshape(-1, 1)),
+        dim=1)
+    print(expected)
+    assert new.labels == label_to_extract
+    assert new.shape[1] == len(label_to_extract)
+    assert torch.all(torch.isclose(expected, new))