I'm thinking you want something like this http://jsfiddle.net/HUbHN/6/
#main{
width: 400px;
height: 400px;
background-color: black;
position:relative;
}
#one {
width: 150px;
height: 100px;
background-color: green;
position:relative;
}
#two {
width: 150px;
height: 150px;
background-color: red;
position:absolute;
top:100px;
}
//js
$("#two").click(function () {
$('#one').animate({'height': '10px', 'top': '99px'}, 1000);
})