<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<!------ Include the above in your HEAD tag ---------->
<!-- -->
<br>
<!-- -->
<div class="well">
Look, I'm in a well!
</div>
<div class="well well-sm">
Look, I'm in a small well!
</div>
<div class="well well-lg">
Look, I'm in a large well!
</div>