diff --git a/docs/graph.html b/docs/graph.html
index fb9bebc3..461a2841 100644
--- a/docs/graph.html
+++ b/docs/graph.html
@@ -24,7 +24,7 @@
 
 <p>
   The graph visualization works smooth on any modern browser for up to a
-  few thousand nodes and edges.
+  few hundred nodes and edges.
 </p>
 
 <p>
@@ -290,6 +290,14 @@ var nodes = [
       the same color schema.</td>
   </tr>
 
+    <tr>
+        <td>fixed</td>
+        <td>Boolean</td>
+        <td>false</td>
+        <td>If fixed is true, then the node will not move from its supplied position.
+            If only an x position has been supplied, it is only fixed in the x-direction.
+            The same holds for y. If both x and y have been defined, the node will not move.</td>
+    </tr>
   <tr>
     <td>fontColor</td>
     <td>String</td>
@@ -827,6 +835,14 @@ var options = {
     <td>"#2B7CE9"</td>
     <td>Default border color of the node when selected.</td>
   </tr>
+    <tr>
+        <td>fixed</td>
+        <td>Boolean</td>
+        <td>false</td>
+        <td>If fixed is true, then the node will not move from its supplied position.
+            If only an x position has been supplied, it is only fixed in the x-direction.
+            The same holds for y. If both x and y have been defined, the node will not move.</td>
+    </tr>
 
   <tr>
     <td>fontColor</td>
@@ -1139,7 +1155,10 @@ var nodes = [
 
 <h3 id="Physics">Physics</h3>
 <p>
-    Graph uses a <a href="http://en.wikipedia.org/wiki/Force-directed_graph_drawing">force directed algorithm</a> to layout nodes and edges, and uses the <a href="http://en.wikipedia.org/wiki/Barnes%E2%80%93Hut_simulation">Barnes-Hut</a> gravitational simulation model. There are a number of configuration options available to tune the physics model. Note that wrong configuration can lead to instable behaviour.
+    The original simulation method was based on particel physics with a repulsion field (potential) around each node,
+    and the edges were modelled as springs. The new system employed the <a href="http://en.wikipedia.org/wiki/Barnes%E2%80%93Hut_simulation">Barnes-Hut</a> gravitational simulation model. The edges are still modelled as springs.
+    To unify the physics system, the damping, repulsion distance and edge length have been combined in an physics option. To retain good behaviour, both the old repulsion model and the Barnes-Hut model have their own parameters.
+    If no options for the physics system are supplied, the Barnes-Hut method will be used with the default parameters.
 </p>
 <pre class="prettyprint">
 // These variables must be defined in an options object named physics.
diff --git a/examples/graph/17_network_info.html b/examples/graph/17_network_info.html
index 0b7e033f..ca97d75a 100644
--- a/examples/graph/17_network_info.html
+++ b/examples/graph/17_network_info.html
@@ -96,11 +96,11 @@
       var x = - mygraph.clientWidth / 2 + 50;
       var y = - mygraph.clientHeight / 2 + 50;
       var step = 70;
-      nodes.push({id: 1000, x: x, y: y, label: 'Internet', group: 'internet', value: 1});
-      nodes.push({id: 1001, x: x, y: y + step, label: 'Switch', group: 'switch', value: 1});
-      nodes.push({id: 1002, x: x, y: y + 2 * step, label: 'Server', group: 'server', value: 1});
-      nodes.push({id: 1003, x: x, y: y + 3 * step, label: 'Computer', group: 'desktop', value: 1});
-      nodes.push({id: 1004, x: x, y: y + 4 * step, label: 'Smartphone', group: 'mobile', value: 1});
+      nodes.push({id: 1000, x: x, y: y, label: 'Internet', group: 'internet', value: 1, fixed:true});
+      nodes.push({id: 1001, x: x, y: y + step, label: 'Switch', group: 'switch', value: 1, fixed:true});
+      nodes.push({id: 1002, x: x, y: y + 2 * step, label: 'Server', group: 'server', value: 1, fixed:true});
+      nodes.push({id: 1003, x: x, y: y + 3 * step, label: 'Computer', group: 'desktop', value: 1, fixed:true});
+      nodes.push({id: 1004, x: x, y: y + 4 * step, label: 'Smartphone', group: 'mobile', value: 1, fixed:true});
 
       // create a graph
       var container = document.getElementById('mygraph');
diff --git a/src/graph/Graph.js b/src/graph/Graph.js
index daa8165b..a170f0fd 100644
--- a/src/graph/Graph.js
+++ b/src/graph/Graph.js
@@ -40,6 +40,7 @@ function Graph (container, data, options) {
       image: undefined,
       widthMin: 16, // px
       widthMax: 64, // px
+      fixed:false,
       fontColor: 'black',
       fontSize: 14, // px
       fontFace: 'verdana',