Tryit Editor v1.8

Source Code:

<!DOCTYPE html>
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">
</script>
<script>
$(document).ready(function()
  {
  $("#btn1").click(function(){
    $("#box").animate({height:"300px"});
  });
  $("#btn2").click(function(){
    $("#box").animate({height:"100px"});
  });
});
</script>
</head>
<body>

<button id="btn1">Animate height</button>
<button id="btn2">Reset height</button>
<div id="box" style="background:#98bf21;height:100px;width:100px;margin:6px;">
</div>

</body>
</html>

Result:

W3Schools.com - Try it yourself

Edit the code above and click "Submit Code" to see the result.