diff --git a/HISTORY.md b/HISTORY.md
index baf7cca3..d5dea88e 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -3,11 +3,17 @@ http://visjs.org
 
 ## not yet released, version 4.4.1-SNAPSHOT
 
+### General
+
+- Docs have been greatly improved thanks to @felixhayashi! Thanks a lot!
+
 ### Network
 
 - Properly fixed the _lockedRedraw method.
 - Fixed node resizing on dragging.
 - Added shapeProperties, thanks @zukomgwili!
+- Fixed missing edges during clustering.
+- Fixed missing refresh of node data when changing hierarchical layout on the fly.
 
 ### Graph3d
 
diff --git a/dist/vis.js b/dist/vis.js
index 2a105fff..24423558 100644
--- a/dist/vis.js
+++ b/dist/vis.js
@@ -5,7 +5,7 @@
  * A dynamic, browser-based visualization library.
  *
  * @version 4.4.1-SNAPSHOT
- * @date    2015-07-10
+ * @date    2015-07-16
  *
  * @license
  * Copyright (C) 2011-2014 Almende B.V, http://almende.com
@@ -13994,7 +13994,7 @@ return /******/ (function(modules) { // webpackBootstrap
   Range.prototype.setOptions = function (options) {
     if (options) {
       // copy the options that we know
-      var fields = ['direction', 'min', 'max', 'zoomMin', 'zoomMax', 'moveable', 'zoomable', 'activate', 'hiddenDates'];
+      var fields = ['direction', 'min', 'max', 'zoomMin', 'zoomMax', 'moveable', 'zoomable', 'activate', 'hiddenDates', 'zoomKey'];
       util.selectiveExtend(fields, this.options, options);
 
       if ('start' in options || 'end' in options) {
@@ -14384,6 +14384,9 @@ return /******/ (function(modules) { // webpackBootstrap
     // only zoom when the mouse is inside the current range
     if (!this._isInsideRange(event)) return;
 
+    // only zoom when the according key is pressed and the zoomKey option is set
+    if (this.options.zoomKey && !event[this.options.zoomKey]) return;
+
     // retrieve delta
     var delta = 0;
     if (event.wheelDelta) {
@@ -18155,6 +18158,11 @@ return /******/ (function(modules) { // webpackBootstrap
       if (subgroup) {
         var itemIndex = subgroup.items.indexOf(item);
         subgroup.items.splice(itemIndex, 1);
+        if (!subgroup.items.length) {
+          delete this.subgroups[item.data.subgroup];
+          this.subgroupIndex--;
+        }
+        this.orderSubgroups();
       }
     }
   };
@@ -20202,37 +20210,40 @@ return /******/ (function(modules) { // webpackBootstrap
     dom.majorTexts = [];
     dom.minorTexts = [];
 
-    var cur;
-    var x = 0;
+    var current;
+    var next;
+    var x;
+    var xNext;
     var isMajor;
-    var xPrev = 0;
-    var width = 0;
-    var prevLine;
-    var prevText;
+    var width;
+    var line;
+    var labelMinor;
     var xFirstMajorLabel = undefined;
     var max = 0;
     var className;
 
     step.first();
+    next = step.getCurrent();
+    xNext = this.body.util.toScreen(next);
     while (step.hasNext() && max < 1000) {
       max++;
 
-      cur = step.getCurrent();
       isMajor = step.isMajor();
       className = step.getClassName();
+      labelMinor = step.getLabelMinor();
 
-      xPrev = x;
-      x = this.body.util.toScreen(cur);
-      width = x - xPrev;
-      if (prevLine) {
-        prevLine.style.width = width + 'px';
-      }
-      if (prevText) {
-        prevText.style.width = width + 'px';
-      }
+      current = next;
+      x = xNext;
+
+      step.next();
+      next = step.getCurrent();
+      xNext = this.body.util.toScreen(next);
+
+      width = xNext - x;
+      var labelFits = labelMinor.length * this.props.minorCharWidth < width;
 
-      if (this.options.showMinorLabels) {
-        prevText = this._repaintMinorText(x, step.getLabelMinor(), orientation, className);
+      if (this.options.showMinorLabels && labelFits) {
+        this._repaintMinorText(x, labelMinor, orientation, className);
       }
 
       if (isMajor && this.options.showMajorLabels) {
@@ -20242,12 +20253,16 @@ return /******/ (function(modules) { // webpackBootstrap
           }
           this._repaintMajorText(x, step.getLabelMajor(), orientation, className);
         }
-        prevLine = this._repaintMajorLine(x, orientation, className);
+        line = this._repaintMajorLine(x, width, orientation, className);
       } else {
-        prevLine = this._repaintMinorLine(x, orientation, className);
+        if (labelFits) {
+          line = this._repaintMinorLine(x, width, orientation, className);
+        } else {
+          if (line) {
+            line.style.width = parseInt(line.style.width) + width + 'px';
+          }
+        }
       }
-
-      step.next();
     }
 
     // create a major label on the left when needed
@@ -20339,12 +20354,13 @@ return /******/ (function(modules) { // webpackBootstrap
   /**
    * Create a minor line for the axis at position x
    * @param {Number} x
+   * @param {Number} width
    * @param {String} orientation   "top" or "bottom" (default)
    * @param {String} className
    * @return {Element} Returns the created line
    * @private
    */
-  TimeAxis.prototype._repaintMinorLine = function (x, orientation, className) {
+  TimeAxis.prototype._repaintMinorLine = function (x, width, orientation, className) {
     // reuse redundant line
     var line = this.dom.redundant.lines.shift();
     if (!line) {
@@ -20362,6 +20378,7 @@ return /******/ (function(modules) { // webpackBootstrap
     }
     line.style.height = props.minorLineHeight + 'px';
     line.style.left = x - props.minorLineWidth / 2 + 'px';
+    line.style.width = width + 'px';
 
     line.className = 'vis-grid vis-vertical vis-minor ' + className;
 
@@ -20371,12 +20388,13 @@ return /******/ (function(modules) { // webpackBootstrap
   /**
    * Create a Major line for the axis at position x
    * @param {Number} x
+   * @param {Number} width
    * @param {String} orientation   "top" or "bottom" (default)
    * @param {String} className
    * @return {Element} Returns the created line
    * @private
    */
-  TimeAxis.prototype._repaintMajorLine = function (x, orientation, className) {
+  TimeAxis.prototype._repaintMajorLine = function (x, width, orientation, className) {
     // reuse redundant line
     var line = this.dom.redundant.lines.shift();
     if (!line) {
@@ -20394,6 +20412,7 @@ return /******/ (function(modules) { // webpackBootstrap
     }
     line.style.left = x - props.majorLineWidth / 2 + 'px';
     line.style.height = props.majorLineHeight + 'px';
+    line.style.width = width + 'px';
 
     line.className = 'vis-grid vis-vertical vis-major ' + className;
 
@@ -22750,6 +22769,7 @@ return /******/ (function(modules) { // webpackBootstrap
     type: { string: string },
     width: { string: string, number: number },
     zoomable: { boolean: boolean },
+    zoomKey: { string: ['ctrlKey', 'altKey', 'metaKey', ''] },
     zoomMax: { number: number },
     zoomMin: { number: number },
 
@@ -22834,6 +22854,7 @@ return /******/ (function(modules) { // webpackBootstrap
       type: ['box', 'point', 'range', 'background'],
       width: '100%',
       zoomable: true,
+      zoomKey: ['ctrlKey', 'altKey', 'metaKey', ''],
       zoomMax: [315360000000000, 10, 315360000000000, 1],
       zoomMin: [10, 10, 315360000000000, 1]
     }
@@ -26191,6 +26212,7 @@ return /******/ (function(modules) { // webpackBootstrap
     },
     width: { string: string, number: number },
     zoomable: { boolean: boolean },
+    zoomKey: { string: ['ctrlKey', 'altKey', 'metaKey', ''] },
     zoomMax: { number: number },
     zoomMin: { number: number },
     __type__: { object: object }
@@ -26292,6 +26314,7 @@ return /******/ (function(modules) { // webpackBootstrap
       start: '',
       width: '100%',
       zoomable: true,
+      zoomKey: ['ctrlKey', 'altKey', 'metaKey', ''],
       zoomMax: [315360000000000, 10, 315360000000000, 1],
       zoomMin: [10, 10, 315360000000000, 1]
     }
@@ -27408,7 +27431,7 @@ return /******/ (function(modules) { // webpackBootstrap
           }
           var data = this.body.data.nodes._data[nodeId];
           if (node !== undefined && data !== undefined) {
-            node.setOptions({ fixed: false });
+            node.setOptions({ fixed: false, x: null, y: null });
             node.setOptions(data);
           }
         }
@@ -27733,11 +27756,20 @@ return /******/ (function(modules) { // webpackBootstrap
         }
 
         // set these options locally
+        // clear x and y positions
         if (options.x !== undefined) {
-          this.x = parseInt(options.x);this.predefinedPosition = true;
+          if (options.x === null) {
+            this.x = undefined;this.predefinedPosition = false;
+          } else {
+            this.x = parseInt(options.x);this.predefinedPosition = true;
+          }
         }
         if (options.y !== undefined) {
-          this.y = parseInt(options.y);this.predefinedPosition = true;
+          if (options.y === null) {
+            this.y = undefined;this.predefinedPosition = false;
+          } else {
+            this.y = parseInt(options.y);this.predefinedPosition = true;
+          }
         }
         if (options.size !== undefined) {
           this.baseSize = options.size;
@@ -37934,6 +37966,11 @@ return /******/ (function(modules) { // webpackBootstrap
           }
 
           if (this.options.hierarchical.enabled === true) {
+            if (prevHierarchicalState === true) {
+              // refresh the overridden options for nodes and edges.
+              this.body.emitter.emit('refresh');
+            }
+
             // make sure the level seperation is the right way up
             if (this.options.hierarchical.direction === 'RL' || this.options.hierarchical.direction === 'DU') {
               if (this.options.hierarchical.levelSeparation > 0) {
diff --git a/lib/network/modules/LayoutEngine.js b/lib/network/modules/LayoutEngine.js
index 464b2841..d663e1bd 100644
--- a/lib/network/modules/LayoutEngine.js
+++ b/lib/network/modules/LayoutEngine.js
@@ -46,6 +46,11 @@ class LayoutEngine {
       }
 
       if (this.options.hierarchical.enabled === true) {
+        if (prevHierarchicalState === true) {
+          // refresh the overridden options for nodes and edges.
+          this.body.emitter.emit('refresh');
+        }
+
         // make sure the level seperation is the right way up
         if (this.options.hierarchical.direction === 'RL' || this.options.hierarchical.direction === 'DU') {
           if (this.options.hierarchical.levelSeparation > 0) {
diff --git a/lib/network/modules/NodesHandler.js b/lib/network/modules/NodesHandler.js
index 40864840..ce5def8d 100644
--- a/lib/network/modules/NodesHandler.js
+++ b/lib/network/modules/NodesHandler.js
@@ -299,7 +299,7 @@ class NodesHandler {
       }
       let data = this.body.data.nodes._data[nodeId];
       if (node !== undefined && data !== undefined) {
-        node.setOptions({ fixed: false });
+        node.setOptions({ fixed: false, x:null, y:null });
         node.setOptions(data);
       }
     }
diff --git a/lib/network/modules/components/Node.js b/lib/network/modules/components/Node.js
index 2ff22d70..d1567e67 100644
--- a/lib/network/modules/components/Node.js
+++ b/lib/network/modules/components/Node.js
@@ -120,8 +120,15 @@ class Node {
 
 
     // set these options locally
-    if (options.x !== undefined)     {this.x = parseInt(options.x); this.predefinedPosition = true;}
-    if (options.y !== undefined)     {this.y = parseInt(options.y); this.predefinedPosition = true;}
+    // clear x and y positions
+    if (options.x !== undefined) {
+      if (options.x === null) {this.x = undefined; this.predefinedPosition = false;}
+      else                    {this.x = parseInt(options.x); this.predefinedPosition = true;}    
+    }
+    if (options.y !== undefined) {
+      if (options.y === null) {this.y = undefined; this.predefinedPosition = false;}
+      else                    {this.y = parseInt(options.y); this.predefinedPosition = true;}
+    }
     if (options.size !== undefined)  {this.baseSize = options.size;}
     if (options.value !== undefined) {options.value = parseFloat(options.value);}
 
diff --git a/test/networkTest.html b/test/networkTest.html
index b34be957..7a948c12 100644
--- a/test/networkTest.html
+++ b/test/networkTest.html
@@ -1,107 +1,148 @@
 <!doctype html>
 <html>
 <head>
-    <title>Network | Clustering</title>
-
-    <script type="text/javascript" src="../dist/vis.js"></script>
-
+    <title>Network | Hierarchical layout</title>
 
     <style type="text/css">
+        body {
+            font: 10pt sans;
+        }
+
         #mynetwork {
             width: 600px;
             height: 600px;
             border: 1px solid lightgray;
         }
-
-        p {
-            max-width: 600px;
-        }
-
-        h4 {
-            margin-bottom: 3px;
-        }
     </style>
-</head>
 
-<body>
+    <script type="text/javascript" src="../dist/vis.js"></script>
 
 
+    <script type="text/javascript">
+        var nodes = null;
+        var edges = null;
+        var network = null;
 
-<div id="mynetwork"></div>
+        function destroy() {
+            if (network !== null) {
+                network.destroy();
+                network = null;
+            }
+        }
 
-<script type="text/javascript">
-    // create an array with nodes
-    var nodes = [
-        {id: 4, label: '4'},
-        {id: 5, label: '5'},
-        {id: 7, label: '7'},
-        {id: 9, label: '9'},
-        {id: 10, label: '10'},
-        {id: 101, label: '101'},
-        {id: 102, label: '102'},
-        {id: 103, label: '103'}
-    ];
-
-    // create an array with edges
-    var edges = [
-        {from: 10, to: 4},
-        {from: 7, to: 5},
-        {from: 9, to: 7},
-        {from: 10, to: 9},
-        {from: 101, to: 102},
-        {from: 102, to: 103}
-    ];
-
-    // create a network
-    var container = document.getElementById('mynetwork');
-    var data = {
-        nodes: nodes,
-        edges: edges
-    };
-    var options = {layout: {randomSeed: 8}};
-    var network = new vis.Network(container, data, options);
+        function draw() {
+            destroy();
+            // randomly create some nodes and edges
+            var nodeCount = document.getElementById('nodeCount').value;
+            //var data = getScaleFreeNetwork(nodeCount)
+            var nodes = [
+                {id: 4, label: '4'},
+                {id: 5, label: '5'},
+                {id: 7, label: '7'},
+                {id: 9, label: '9'},
+                {id: 10, label: '10'},
+                {id: 101, label: '101'},
+                {id: 102, label: '102'},
+                {id: 103, label: '103'}
+            ];
+
+            // create an array with edges
+            var edges = [
+                {from: 10, to: 4},
+                {from: 7, to: 5},
+                {from: 9, to: 7},
+                {from: 10, to: 9},
+                {from: 101, to: 102},
+                {from: 102, to: 103}
+            ];
+
+            var data = {
+                nodes: nodes,
+                edges: edges
+            };
+            // create a network
+            var container = document.getElementById('mynetwork');
+            var directionInput = document.getElementById("direction").value;
+            var options = {
+                interaction: {
+                    navigationButtons: true
+                },
+                layout: {
+                    hierarchical: {
+                        direction: directionInput
+                    }
+                }
+            };
+            network = new vis.Network(container, data, options);
+
+            // add event listeners
+            network.on('select', function (params) {
+                document.getElementById('selection').innerHTML = 'Selection: ' + params.nodes;
+            });
+        }
 
+        function changeOptions(directionInputValue) {
+            network.setOptions({
+                layout: {
+                    hierarchical: {
+                        direction: directionInputValue
+                    }
+                }
+            });
+        }
 
+    </script>
+</head>
 
-    // if we click on a node, we want to open it up!
-    network.on("selectNode", function (params) {
-        if (params.nodes.length == 1) {
-            if (network.isCluster(params.nodes[0]) == true) {
-                network.openCluster(params.nodes[0])
-            }
-        }
-    });
-
-    function a() {
-        var clusterOptionsByData = {
-            joinCondition: function (node) {
-                if (node.id == 4 || node.id == 101)
-                    return true;
-                return false;
-            },
-            clusterNodeProperties: {id: "c1", label: 'c1'}
-        }
-        network.cluster(clusterOptionsByData);
+<body onload="draw();">
+<h2>Hierarchical Layout - Scale-Free-Network</h2>
+
+<div style="width:700px; font-size:14px; text-align: justify;">
+    This example shows the randomly generated <b>scale-free-network</b> set of nodes and connected edges from example 2.
+    In this example, hierarchical layout has been enabled and the vertical levels are determined automatically.
+</div>
+<br/>
+
+<form onsubmit="draw(); return false;">
+    <label for="nodeCount">Number of nodes:</label>
+    <input id="nodeCount" type="text" value="25" style="width: 50px;">
+    <input type="submit" value="Go">
+</form>
+<p>
+    <input type="button" id="btn-UD" value="Up-Down">
+    <input type="button" id="btn-DU" value="Down-Up">
+    <input type="button" id="btn-LR" value="Left-Right">
+    <input type="button" id="btn-RL" value="Right-Left">
+    <input type="hidden" id='direction' value="UD">
+</p>
+
+<script language="javascript">
+    var directionInput = document.getElementById("direction");
+    var btnUD = document.getElementById("btn-UD");
+    btnUD.onclick = function () {
+        directionInput.value = "UD";
+        changeOptions(directionInput.value);
     }
-
-   function b() {
-       var clusterOptionsByData2 = {
-           joinCondition: function (node) {
-               if (node.id == 'c1' || node.id == 5)
-                   return true;
-               return false;
-           },
-           clusterNodeProperties: {id: "c2", label: 'c2'}
-       }
-       network.cluster(clusterOptionsByData2);
-   }
-
-    a()
-    b()
-    network.openCluster("c2")
+    var btnDU = document.getElementById("btn-DU");
+    btnDU.onclick = function () {
+        directionInput.value = "DU";
+        changeOptions(directionInput.value);
+    };
+    var btnLR = document.getElementById("btn-LR");
+    btnLR.onclick = function () {
+        directionInput.value = "LR";
+        changeOptions(directionInput.value);
+    };
+    var btnRL = document.getElementById("btn-RL");
+    btnRL.onclick = function () {
+        directionInput.value = "RL";
+        changeOptions(directionInput.value);
+    };
 </script>
-<input type="button" value="a" onclick="a()">
-<input type="button" value="b" onclick="b()">
+<br>
+
+<div id="mynetwork"></div>
 
+<p id="selection"></p>
 </body>
 </html>