diff --git a/_posts/tests/2011-10-19-callbacks.html b/_posts/tests/2011-10-19-callbacks.html
new file mode 100644
index 0000000..aac3601
--- /dev/null
+++ b/_posts/tests/2011-10-19-callbacks.html
@@ -0,0 +1,165 @@
+---
+title: Callbacks
+layout: default
+category: tests
+---
+
+<section id="copy">
+  <p>Tests that callbacks are triggering properly, after animation/transition has completed.</p>
+
+</section>
+
+<section id="options" class="clearfix">
+
+  {% include filter-buttons.html %}
+
+  {% include sort-buttons.html %}
+
+  <h3>Etc</h3>
+
+  <ul id="etc" class="clearfix">
+    <li id="toggle-sizes"><a href="#toggle-sizes">Toggle variable sizes</a></li>
+    <li id="insert"><a href="#insert">Insert new elements</a></li>
+    <li id="append"><a href='#append'>Append new elements</a></li>
+    <li id="shuffle"><a href='#shuffle'>Shuffle</a></li>
+  </ul>
+
+</section> <!-- #options -->
+
+<div id="container" class="clickable variable-sizes clearfix">
+  {% for elem_number in site.best_of_order %}
+    {% assign element = site.elements[elem_number] %}
+    {% include element-partial.html %}
+  {% endfor %}
+</div> <!-- #container -->
+
+
+<script src="../{{ site.jquery_js }}"></script>
+<script src="../{{ site.isotope_js }}"></script>
+<script src="../js/fake-element.js"></script>
+<script>
+
+  $(function(){
+    
+    var $container = $('#container');
+    
+    {% include random-sizes.js %}
+    
+    var colors = ['red', 'green', 'blue', 'yellow', 'purple', 'orange', 'white'],
+        colorI = 0;
+
+    function changeBGColor() {
+      var color = colors[ colorI % colors.length ];
+      $container.css({ background: color })
+      colorI++;
+    }
+    
+    $container.isotope({
+      itemSelector : '.element',
+      masonry : {
+        columnWidth : 120
+      },
+      masonryHorizontal : {
+        rowHeight: 120
+      },
+      cellsByRow : {
+        columnWidth : 240,
+        rowHeight : 240
+      },
+      cellsByColumn : {
+        columnWidth : 240,
+        rowHeight : 240
+      },
+      getSortData : {
+        symbol : function( $elem ) {
+          return $elem.attr('data-symbol');
+        },
+        category : function( $elem ) {
+          return $elem.attr('data-category');
+        },
+        number : function( $elem ) {
+          return parseInt( $elem.find('.number').text(), 10 );
+        },
+        weight : function( $elem ) {
+          return parseFloat( $elem.find('.weight').text().replace( /[\(\)]/g, '') );
+        },
+        name : function ( $elem ) {
+          return $elem.find('.name').text();
+        }
+      }
+    }, changeBGColor );
+      
+
+    var $optionSets = $('#options .option-set'),
+        $optionLinks = $optionSets.find('a');
+    
+    $optionLinks.click(function(){
+      var $this = $(this);
+      // don't proceed if already selected
+      if ( $this.hasClass('selected') ) {
+        return false;
+      }
+      var $optionSet = $this.parents('.option-set');
+      $optionSet.find('.selected').removeClass('selected');
+      $this.addClass('selected');
+
+      // make option object dynamically, i.e. { filter: '.my-filter-class' }
+      var options = {},
+          key = $optionSet.attr('data-option-key'),
+          value = $this.attr('data-option-value');
+      // parse 'false' as false boolean
+      value = value === 'false' ? false : value;
+      options[ key ] = value;
+      if ( key === 'layoutMode' && typeof changeLayoutMode === 'function' ) {
+        // changes in layout modes need extra logic
+        changeLayoutMode( $this, options )
+      } else {
+        // otherwise, apply new options
+        $container.isotope( options, changeBGColor );
+      }
+      
+      return false;
+    });
+
+
+
+    $('#insert a').click(function(){
+      var $newEls = $( fakeElement.getGroup() );
+      $container.isotope( 'insert', $newEls, changeBGColor );
+
+      return false;
+    });
+
+    $('#append a').click(function(){
+      var $newEls = $( fakeElement.getGroup() );
+      $container.append( $newEls ).isotope( 'appended', $newEls, changeBGColor );
+
+      return false;
+    });
+
+
+    // change size of clicked element
+    $container.delegate( '.element', 'click', function(){
+      $(this).toggleClass('large');
+      $container.isotope('reLayout');
+    });
+
+    // toggle variable sizes of all elements
+    $('#toggle-sizes').find('a').click(function(){
+      $container
+        .toggleClass('variable-sizes')
+        .isotope('reLayout');
+      return false;
+    });
+
+
+    var $sortBy = $('#sort-by');
+    $('#shuffle a').click(function(){
+      $container.isotope('shuffle');
+      $sortBy.find('.selected').removeClass('selected');
+      $sortBy.find('[data-option-value="random"]').addClass('selected');
+      return false;
+    });
+    
+  });
+</script>
\ No newline at end of file
diff --git a/jquery.isotope.js b/jquery.isotope.js
index b00de57..38a5e29 100644
--- a/jquery.isotope.js
+++ b/jquery.isotope.js
@@ -1,5 +1,5 @@
 /**
- * Isotope v1.4.110906
+ * Isotope v1.5.0 beta
  * An exquisite jQuery plugin for magical layouts
  * http://isotope.metafizzy.co
  *
@@ -45,7 +45,9 @@
     }
   }
 
-  var transformProp = getStyleProperty('transform');
+  var transformProp = getStyleProperty('transform'),
+      transitionProp = getStyleProperty('transitionProperty');
+      
 
   // ========================= miniModernizr ===============================
   // <3<3<3 and thanks to Faruk and Paul for doing the heavy lifting
@@ -92,7 +94,7 @@
     },
 
     csstransitions: function() {
-      return !!getStyleProperty('transitionProperty');
+      return !!transitionProp;
     }
   };
 
@@ -247,8 +249,20 @@
     };
 
   }
+  
+  // ========================= get transition-end event ===============================
+  
+  if ( Modernizr.csstransitions ) {
+    var transitionEndEvent = {
+      WebkitTransitionProperty: 'webkitTransitionEnd',  // webkit
+      MozTransitionProperty: 'transitionend',
+      OTransitionProperty: 'oTransitionEnd',
+      transitionProperty: 'transitionEnd'
+    }[ transitionProp ];
+    var transitionDurProp = getStyleProperty('transitionDuration');
+  }
 
-
+  // ========================= smartresize ===============================
 
   /*
    * smartresize: debounced resize event for jQuery
@@ -295,11 +309,11 @@
 
 
   // our "Widget" object constructor
-  $.Isotope = function( options, element ){
+  $.Isotope = function( options, element, callback ){
     this.element = $( element );
 
     this._create( options );
-    this._init();
+    this._init( callback );
   };
   
   // styles of container element we want to keep track of
@@ -423,7 +437,6 @@
       
       this.$filteredAtoms = this._filter( this.$allAtoms );
       this._sort();
-      
       this.reLayout( callback );
 
     },
@@ -588,17 +601,12 @@
         this.styleQueue.push({ $el: this.element, style: containerStyle });
       }
 
-      this._processStyleQueue();
-
-      // provide $elems as context for the callback
-      if ( callback ) {
-        callback.call( $elems );
-      }
+      this._processStyleQueue( $elems, callback );
       
       this.isLaidOut = true;
     },
     
-    _processStyleQueue : function() {
+    _processStyleQueue : function( $elems, callback ) {
       // are we animating the layout arrangement?
       // use plugin-ish syntax for css or animate
       var styleFn = !this.isLaidOut ? 'css' : (
@@ -606,13 +614,67 @@
           ),
           animOpts = this.options.animationOptions,
           _isInsertingAnimated = this._isInserting && this.isUsingJQueryAnimation,
-          objStyleFn;
-      
+          objStyleFn, processor,
+          triggerCallbackNow, callbackFn;
+
+      // default styleQueue processor, may be overwritten down below
+      processor = function( i, obj ) {
+        obj.$el[ styleFn ]( obj.style, animOpts );
+      };
+
+      if ( this._isInserting || !callback ) {
+        // process styleQueue
+        processor = function( i, obj ) {
+          // only animate if it not being inserted
+          objStyleFn = _isInsertingAnimated && obj.$el.hasClass('no-transition') ? 'css' : styleFn;
+          obj.$el[ objStyleFn ]( obj.style, animOpts );
+        };
+        
+      } else {
+        var isCallbackTriggered = false;
+        callbackFn = function() {
+          // trigger callback only once
+          if ( isCallbackTriggered ) {
+            return;
+          }
+          callback( $elems );
+          isCallbackTriggered = true;
+        };
+        
+        if ( this.isUsingJQueryAnimation ) {
+          // add callback to animation options
+          animOpts.complete = callbackFn;
+        } else if ( Modernizr.csstransitions ) {
+          // detect if first item has transition
+          var i = 0,
+              testElem = this.styleQueue[0].$el;
+          // get first non-empty jQ object
+          // console.log( this.styleQueue )
+          if ( !testElem.length ) {
+            return;
+          }
+          // get transition duration of the first element in that object
+          // yeah, this is inexact
+          var duration = parseFloat( getComputedStyle( testElem[0] )[ transitionDurProp ] );
+          if ( duration > 0 ) {
+            processor = function( i, obj ) {
+              obj.$el[ styleFn ]( obj.style, animOpts )
+                // trigger callback at transition end
+                .one( transitionEndEvent, callbackFn );
+            }
+          } else {
+            // no transition? hit it now, son
+            triggerCallbackNow = true;
+          }
+        }
+      }
+
       // process styleQueue
-      $.each( this.styleQueue, function( i, obj ) {
-        objStyleFn = _isInsertingAnimated && obj.$el.hasClass('no-transition') ? 'css' : styleFn;
-        obj.$el[ objStyleFn ]( obj.style, animOpts );
-      });
+      $.each( this.styleQueue, processor );
+      
+      if ( triggerCallbackNow ) {
+        callbackFn()
+      }
 
       // clear out queue for next time
       this.styleQueue = [];
@@ -695,11 +757,8 @@
         $newAtoms.removeClass('no-transition');
         // reveal newly inserted filtered elements
         instance.styleQueue.push({ $el: $newAtoms, style: instance.options.visibleStyle });
-        instance._processStyleQueue();
-        delete instance._isInserting;
-        if ( callback ) {
-          callback( $newAtoms );
-        }
+        instance._isInserting = false;
+        instance._processStyleQueue( $newAtoms, callback );
       }, 10 );
     },
     
@@ -1246,7 +1305,7 @@
   // A bit from jcarousel 
   //   https://github.com/jsor/jcarousel/blob/master/lib/jquery.jcarousel.js
 
-  $.fn.isotope = function( options ) {
+  $.fn.isotope = function( options, callback ) {
     if ( typeof options === 'string' ) {
       // call method
       var args = Array.prototype.slice.call( arguments, 1 );
@@ -1271,10 +1330,10 @@
         if ( instance ) {
           // apply options & init
           instance.option( options );
-          instance._init();
+          instance._init( callback );
         } else {
           // initialize new instance
-          $.data( this, 'isotope', new $.Isotope( options, this ) );
+          $.data( this, 'isotope', new $.Isotope( options, this, callback ) );
         }
       });
     }