diff --git a/mapytex/calculus/API/expression.py b/mapytex/calculus/API/expression.py
index bc897d0..196ae0e 100644
--- a/mapytex/calculus/API/expression.py
+++ b/mapytex/calculus/API/expression.py
@@ -10,6 +10,7 @@
 Expression
 
 """
+from functools import partial
 from ..core import AssocialTree, Tree, compute, typing, TypingError
 from ..core.random import extract_rdleaf, extract_rv, random_generator, compute_leafs, replace_rdleaf
 from ..core.MO import moify
@@ -438,6 +439,45 @@ class Expression(object):
         else:
             yield self
 
+    def __call__(self, value):
+        """ Call a Expression to evaluate itself on value 
+
+        :examples:
+        >>> f = Expression.from_str("3*x^2 + 2x + 1")
+        >>> for s in f(2).explain():
+        ...     print(s)
+        3 * 2^2 + 2 * 2 + 1
+        3 * 4 + 4 + 1
+        12 + 5
+        17
+        """
+        tree = self._tree
+        variable = (set(tree.get_leafs(extract_variable)) - {None}).pop()
+
+        dest = moify(value)
+        replace_var = partial(replace, origin=variable, dest=dest)
+        tree = tree.map_on_leaf(replace_var)
+
+        return Expression(tree).simplify()
+
+
+def extract_variable(leaf):
+    try:
+        return leaf.variable
+    except AttributeError:
+        return None
+
+def replace(leaf, origin, dest):
+    """ Recursively replace origin to dest in leaf """
+    try:
+        leaf.tree
+    except AttributeError:
+        if leaf == origin:
+            return dest
+        return leaf
+
+    replace_var = partial(replace, origin=origin, dest=dest)
+    return leaf.tree.map_on_leaf(replace_var)
 
 # -----------------------------
 # Reglages pour 'vim'
diff --git a/mapytex/calculus/API/tokens/polynomial.py b/mapytex/calculus/API/tokens/polynomial.py
index 3b09f8a..a1dfc11 100644
--- a/mapytex/calculus/API/tokens/polynomial.py
+++ b/mapytex/calculus/API/tokens/polynomial.py
@@ -11,7 +11,6 @@ Tokens representing polynomials functions
 
 """
 from ..expression import Expression
-from functools import partial
 from .token import Token
 from ...core.MO import MO
 from ...core.MO.atoms import moify
@@ -93,14 +92,7 @@ class Polynomial(Token):
         12 + 5
         17
         """
-        tree = self._mo.tree
-        variable = (set(tree.get_leafs(extract_variable)) - {None}).pop()
-
-        dest = moify(value)
-        replace_var = partial(replace, origin=variable, dest=dest)
-        tree = tree.map_on_leaf(replace_var)
-
-        return Expression(tree).simplify()
+        return Expression(self._mo.tree)(value)
     
     def differentiate(self):
         """ Differentiate a polynome
@@ -262,25 +254,6 @@ class Quadratic(Polynomial):
         else:
             raise NotImplementedError("Todo!")
 
-
-
-def extract_variable(leaf):
-    try:
-        return leaf.variable
-    except AttributeError:
-        return None
-
-def replace(leaf, origin, dest):
-    """ Recursively replace origin to dest in leaf """
-    try:
-        leaf.tree
-    except AttributeError:
-        if leaf == origin:
-            return dest
-        return leaf
-
-    replace_var = partial(replace, origin=origin, dest=dest)
-    return leaf.tree.map_on_leaf(replace_var)
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4: