diff --git a/slither/core/dominators/node_dominator_tree.py b/slither/core/dominators/node_dominator_tree.py
new file mode 100644
index 000000000..046acc439
--- /dev/null
+++ b/slither/core/dominators/node_dominator_tree.py
@@ -0,0 +1,37 @@
+'''
+    Nodes of the dominator tree
+'''
+
+from slither.core.children.child_function import ChildFunction
+
+class DominatorNode(object):
+
+    def __init__(self):
+        self._succ = set()
+        self._nodes = []
+
+    def add_node(self, node):
+        self._nodes.append(node)
+
+    def add_successor(self, succ):
+        self._succ.add(succ)
+
+    @property
+    def cfg_nodes(self):
+        return self._nodes
+
+    @property
+    def sucessors(self):
+        '''
+            Returns:
+                dict(Node)
+        '''
+        return self._succ
+
+class DominatorTree(ChildFunction):
+
+    def __init__(self, entry_point):
+        super(DominatorTree, self).__init__()
+        
+
+        
diff --git a/slither/slithir/operations/phi_callback.py b/slither/slithir/operations/phi_callback.py
new file mode 100644
index 000000000..ba30088a7
--- /dev/null
+++ b/slither/slithir/operations/phi_callback.py
@@ -0,0 +1,41 @@
+import logging
+
+from slither.core.variables.variable import Variable
+from slither.slithir.variables import TupleVariable
+from slither.core.declarations.function import Function
+from slither.slithir.utils.utils import is_valid_lvalue, is_valid_rvalue
+from .phi import Phi
+
+class PhiCallback(Phi):
+
+    def __init__(self, left_variable, nodes):
+        assert is_valid_lvalue(left_variable)
+        assert isinstance(nodes, set)
+        super(PhiCallback, self).__init__(left_variable, nodes)
+
+    @property
+    def read(self):
+        return [self.rvalues]
+
+    @property
+    def rvalues(self):
+        return self._rvalues
+
+    @property
+    def rvalue_no_callback(self):
+        '''
+            rvalue if callback are not considered
+        '''
+        return self._rvalues[0]
+
+    @rvalues.setter
+    def rvalues(self, vals):
+        self._rvalues = vals
+
+
+    @property
+    def nodes(self):
+        return self._nodes
+
+    def __str__(self):
+        return '{}({}) := \u03D5({})'.format(self.lvalue, self.lvalue.type, [v.ssa_name for v in self._rvalues])