diff --git a/README.md b/README.md
index 0589be3..5480f06 100644
--- a/README.md
+++ b/README.md
@@ -38,26 +38,31 @@ Add the component in your vue view.
 
 ## Node Options
 
+  `[opt]` means optional property.
+
 ```javascript
 {
   name: 'Node Name',
   title: 'Node Tag title attr',
-  isParent: true, //
-  isOpen: true, // Control node to fold or unfold
-  icon: 'fa fa-folder', // Or other custom icons call by class name
-  openedIcon: 'fa fa-folder-open', // [option] For parent. Show when isOpen == true, show icon if it's null or empty 
-  closedIcon: 'fa fa-folder', // [option] For parent. Show when isOpen != true, show icon if it's null or empty 
-  children: [], // for parent node only
-  buttons: [ // []
+  isParent: true, // Requested for parent node
+  isOpen: false, // [opt] Control node to fold or unfold
+  icon: 'fa fa-folder', //[opt] Icon class name
+  openedIcon: 'fa fa-folder-open', // [opt] For parent. Show when isOpen == true, show icon if it's null or empty 
+  closedIcon: 'fa fa-folder', // [opt] For parent. Show when isOpen != true, show icon if it's null or empty 
+  children: [], // Requested for parent node
+  buttons: [ // [opt]
     {
-      title: 'icon button tag title attr', //[option]
+      title: 'icon button tag title attr', //[opt]
       icon: 'fa fa-edit',
-      click: function (node) { //[option]
+      click: function (node) { //[opt]
           //
       }
     }
     //...
-  ]
+  ],
+  showLoading: false, // [opt] For parent, when `node.showLoading && node._loading` and node is opened then show loading icon
+  onOpened: function (node) {}, // [opt]
+  onClosed: function (node) {} // [opt]
 }
 ```
 
diff --git a/demo/demo.js b/demo/demo.js
index 3fb5eb7..7e6f31e 100644
--- a/demo/demo.js
+++ b/demo/demo.js
@@ -5,7 +5,6 @@
         node.children.push({
             name: 'child node',
             parent: node,
-            isOpen: true,
             isParent: true,
             children: [],
             buttons: [
@@ -78,7 +77,6 @@
                         },
                         {
                             name: 'Level1 add node',
-                            isOpen: true,
                             isParent: true,
                             children: [],
                             buttons: [
@@ -88,7 +86,7 @@
                                     click: function (node) {
                                         node.isOpen = true;
                                         node.children.push({
-                                            name: 'level2 node',
+                                            name: 'Level2 node',
                                             parent: node,
                                             buttons: [
                                                 {
@@ -105,8 +103,7 @@
                             ]
                         },
                         {
-                            name: 'level1-addNode',
-                            isOpen: true,
+                            name: 'Level1-addNode',
                             isParent: true,
                             children: [],
                             buttons: [
@@ -116,6 +113,27 @@
                                     click: addNode
                                 }
                             ]
+                        },
+                        {
+                            name: 'Level1 Ajax',
+                            isParent: true,
+                            children: [],
+                            showLoading: true, // if (node.showLoading && node._loading) then show loading icon
+                            onOpened: function (node) {
+                                if (!node._loading) {
+                                    Vue.set(node, 'children', []); // Clean old data
+                                    node._loading = true; // Start Ajax
+                                    setTimeout(function () { //
+                                        node._loading = false; //Finish Ajax
+                                        for (var i = 1; i < 6; i++) {
+                                            node.children.push({name: 'Ajax Node ' + i});
+                                        }
+                                    }, 2000);
+                                }
+                            },
+                            onClosed: function () {
+                                // NOOP
+                            }
                         }
                     ]
                 }
diff --git a/src/tree.vue.js b/src/tree.vue.js
index abb7b14..c3d6dca 100644
--- a/src/tree.vue.js
+++ b/src/tree.vue.js
@@ -2,11 +2,12 @@
     'use strict';
     var VueTreeItem = Vue.extend({
         template: '<li :class="{parent_li: node.isParent}">' +
-        '<i v-if="node.isParent" v-on:click="click(node)" class="fa icon-open-state" :class=\'{"fa-plus-square-o": !node.isOpen, "fa-minus-square-o": node.isOpen}\'></i>' +
+        '<i v-if="node.isParent" v-on:click="toggle(node)" class="fa icon-open-state" :class=\'{"fa-plus-square-o": !node.isOpen, "fa-minus-square-o": node.isOpen}\'></i>' +
         '<span :title="node.title">' +
         '<i v-if="showIcon(node)" :class="nodeClass(node)"></i> {{node.name}}</span>' +
         '<a v-for="btn in node.buttons" class="ml5" href="javascript:" :title="btn.title" v-on:click="btnClick(btn, node)"><i :class="btn.icon"></i></a>' +
-        '<ul v-if="node.children && node.children.length" v-show="node.isOpen">' +
+        '<ul v-show="node.isOpen">' +
+        '<li v-show="node.showLoading && node._loading"><i class="fa fa-spinner fa-pulse"></i></li>' +
         '<vue-tree-item v-for="item in node.children" :node="item"></vue-tree-item>' +
         '</ul>' +
         '</li>',
@@ -26,14 +27,34 @@
                     return node.closedIcon || node.icon;
                 }
             },
-            click: function (node) {
-                node.isOpen = !node.isOpen;
+            toggle: function (node) {
+                if (node.hasOwnProperty('isOpen')) {
+                    node.isOpen = !node.isOpen;
+                } else {
+                    Vue.set(node, 'isOpen', true);
+                }
             },
             btnClick: function (btn, node) {
                 if (typeof btn.click === 'function') {
                     btn.click(node);
                 }
             }
+        },
+        watch: {
+            'node.isOpen': function (val) {
+                if (!this.node.hasOwnProperty('_loading')) {
+                    Vue.set(this.node, '_loading', false);
+                }
+                if (val) {
+                    if (typeof this.node.onOpened === 'function') {
+                        this.node.onOpened(this.node);
+                    }
+                } else {
+                    if (typeof this.node.onClosed === 'function') {
+                        this.node.onClosed(this.node);
+                    }
+                }
+            }
         }
     });
     Vue.component('vue-tree-item', VueTreeItem);