diff --git a/README.md b/README.md
index cc59d36..57c5933 100644
--- a/README.md
+++ b/README.md
@@ -98,6 +98,11 @@ There ist still quite some work to do.
 And for all others, don't hesitate to open issues when you have problems!
 
 ## Changelog
+#### 1.0.4
+- Adds active state for automaton
+- Adds reactivation method
+- Fixes cells active state
+
 #### 1.0.3
 - Fixes init_cell_state called twice the necessary amount
 
diff --git a/cellular_automaton/automaton.py b/cellular_automaton/automaton.py
index 83eb6e6..bc73b15 100644
--- a/cellular_automaton/automaton.py
+++ b/cellular_automaton/automaton.py
@@ -86,6 +86,17 @@ class CellularAutomaton(CellularAutomatonCreator, abc.ABC):
     def __init__(self, neighborhood: Neighborhood, *args, **kwargs):
         super().__init__(neighborhood=neighborhood, *args, **kwargs)
         self._evolution_step = 0
+        self._active = True
+
+    def is_active(self):
+        return self._active
+
+    def reactivate(self):
+        """ Sets all cells active again """
+        for cell in self._current_state.values():
+            cell.is_active = True
+
+    active = property(is_active)
 
     def get_cells(self):
         return self._current_state
@@ -109,6 +120,7 @@ class CellularAutomaton(CellularAutomatonCreator, abc.ABC):
         :param times: The number of evolution steps processed with one call of this method.
         """
         for _ in itertools.repeat(None, times):
+            self._active = False
             self.__evolve_cells(self._current_state, self._next_state)
             self._current_state, self._next_state = self._next_state, self._current_state
             self._evolution_step += 1
@@ -122,12 +134,12 @@ class CellularAutomaton(CellularAutomatonCreator, abc.ABC):
                 old.is_active = False
                 evolve_cell(old, new, new_state)
 
-    @classmethod
-    def __evolve_cell(cls, old, cell, new_state):
-        changed = new_state != cell.state
+    def __evolve_cell(self, old, cell, new_state):
+        changed = new_state != old.state
         cell.state = new_state
         cell.is_dirty |= changed
         old.is_dirty |= changed
+        self._active |= changed
         if changed:
             cell.is_active = True
             for n in cell.neighbors:
diff --git a/setup.py b/setup.py
index 2f8e15b..ccdd9ce 100644
--- a/setup.py
+++ b/setup.py
@@ -7,7 +7,7 @@ with open('README.md') as f:
 
 setup(
     name="cellular_automaton",
-    version="1.0.3",
+    version="1.0.4",
     author="Richard Feistenauer",
     author_email="r.feistenauer@web.de",
     packages=find_packages(exclude=('tests', 'docs', 'examples')),
diff --git a/tests/test_automaton.py b/tests/test_automaton.py
index 98d0f42..f5ee7cf 100644
--- a/tests/test_automaton.py
+++ b/tests/test_automaton.py
@@ -15,7 +15,7 @@ limitations under the License.
 """
 
 # pylint: disable=missing-function-docstring
-# pylint: disable=redefined-outer-name
+# pylint: disable=missing-class-docstring
 
 import pytest
 
@@ -23,11 +23,11 @@ from .context import cellular_automaton as ca
 
 
 class TAutomaton(ca.CellularAutomaton):
-    """ Simple Automaton for test purposes """
-    def evolve_rule(self, last_cell_state, neighbors_last_states):
+
+    def evolve_rule(self, last_cell_state, __):
         return [last_cell_state[0] + 1]
 
-    def init_cell_state(self, cell_coordinate):
+    def init_cell_state(self, __):
         return [0]
 
 
@@ -53,9 +53,31 @@ def test_dimensions(dimensions):
     assert automaton.cells[(1, ) * dimensions].state[0] == 1
 
 
-def test_process_evolution_calls():
+def test_copy_cells():
     automaton = TAutomaton(NEIGHBORHOOD, [3, 3])
     automaton.evolve(5)
     automaton2 = TAutomaton(NEIGHBORHOOD, [3, 3])
     automaton2.cells = automaton.cells
     assert automaton2.cells[(1, 1)].state[0] == 5
+
+
+def test_automaton_goes_inactive():
+    automaton = TAutomaton(NEIGHBORHOOD, [3, 3])
+    assert automaton.active
+
+    automaton.evolve_rule = lambda x, y: x
+    automaton.evolve()
+    assert not automaton.active
+
+
+def test_reactivation():
+    automaton = TAutomaton(NEIGHBORHOOD, [3, 3])
+
+    rule, automaton.evolve_rule = automaton.evolve_rule, lambda x, y: x
+    automaton.evolve()
+    assert not automaton.active
+
+    automaton.reactivate()
+    automaton.evolve_rule = rule
+    automaton.evolve()
+    assert automaton.active