<div id="small"></div><div id="large"></div>

#small{    width: 100px;    height: 100px;    background: red;    position: absolute;    top: 100px;    left: 100px;}#large{    width: 200px;    height: 200px;    background: purple;    position: absolute;    left: 500px;    top: 300px;}

$(function(){    $("#small").mouseover(function(){        $("#large").stop().animate({            width: "1000px"        });    });    $("#small").mouseout(function(){        $("#large").stop().animate({            width: "200px"        });    });});