Edit in JSFiddle

window.addEvent('domready', function(){

     /*JavaScript原生的鼠标事件:mouseover , mouseout , mousemove*/    
     $('parent').addEvents({
        //当鼠标指针悬停于某元素之上时执行脚本
        'mouseover':function(event){
           $('print').set('html','mouseover, '+'X:' + event.client.x + ' Y:' + event.client.y);        
        },
        //当鼠标指针移出某元素时执行脚本
        'mouseout':function(event){
            $('print').set('html','mouseout, '+'X:' + event.client.x + ' Y:' + event.client.y);    
        },
        //当鼠标指针移动时执行脚本
        'mousemove':function(event){
            $('print').set('html','mousemove, '+'X:' + event.client.x + ' Y:' + event.client.y);
        }    
     });
     /*MooTools扩展的自定义事件:mouseenter , mouseleave , mousewheel */    
     $('parent1').addEvents({
         //mouseenter 鼠标进入DOM元素的区域后触发。不会在经过子元素的时候触发(不像 mouseover)。
        'mouseenter':function(event){
           $('print1').set('html','mouseenter, '+'X:' + event.client.x + ' Y:' + event.client.y);        
        
        },
        
        //mouseleave 鼠标离开DOM元素的区域后触发。不会在经过子元素的时候触发(不像 mouseout)。
        'mouseleave':function(event){
           $('print1').set('html','mouseleave, '+'X:' + event.client.x + ' Y:' + event.client.y);        
         },
        
        //本事件在鼠标滚轮滚动时触发
        'mousewheel':function(event){
        
            $('print1').set('html','mousewheel, '+'X:' + event.client.x + ' Y:' + event.client.y);        
        
        }
        
     });
     /*mouseenter 和 mouseleave 的综合应用 */                                 
     $('parent2').addEvents({
        'mouseenter': function(){
            this.set('tween', {
                duration: 1000,
                transition: Fx.Transitions.Bounce.easeOut
            }).tween('height', '200px');
        },
        'mouseleave': function(){
            this.set('tween', {}).tween('height', '20px');
        }
     }); 
  
});
<div class="box">
    <div id="print"></div>
    <div id="parent"> 
      <div id="children">子元素</div>
      父元素
    </div>
    <p><strong>JavaScript原生的鼠标事件:</strong>mouseover , mouseout , mousemove</p>
</div>
<div class="box">
    <div id="print1"></div>
    <div id="parent1"> 
      <div id="children">子元素</div>
      父元素
    </div>
    <p><strong>MooTools扩展的自定义事件:</strong>mouseenter , mouseleave , mousewheel</p>
</div>
<div class="box">
    <div id="parent2">  </div>
    <p>mouseenter 和 mouseleave 的综合应用</p>
</div>
.box{
    float: left;
    margin-left: 100px;
    text-align: center;
    padding: 10px;
    width: 200px;
}
#parent,#parent1,#parent2{
    height: 200px;
    width: 200px;
    background-color: #FAA;
    text-align: right;
    margin-bottom: 20px;
}
#children{
    height: 100px;
    width: 100px;
    background-color: #8ACC00;
    padding: 0px;
    text-align: right;
}
#print,#print1{
    background-color: #000;
    color: #FFF;
    height: 20px;
    width: 200px;
    margin-top: 20px;
    margin-bottom: 20px;
    text-align: center;
    font-family: Verdana, Geneva, sans-serif;
    font-size: 12px;
    line-height: 20px;
}