JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.1.1/css/bootstrap.min.css">
<div class="container-fluid">
  <div class="row-fluid">
    <div class="span12 red">
       Red area here.
       <div class="row-fluid">
          <div class="span6 blue">
            Small box
          </div>
          <div class="span6 blue">
            Small box
          </div>
       </div>
    </div>
  </div>
</div>

CSS

.red {background-color: red}
.blue {background-color: blue}