JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/bootstrap/3.1.0/css/bootstrap.min.css">
  <div class="row">
    <div class="col-sm-12 red">
       Red area here.
       <div class="row">
          <div class="col-sm-6 blue">
            Small box
          </div>
          <div class="col-sm-6 blue">
            Small box
          </div>
       </div>
    </div>
  </div>

<p>Make sure this window is wide enough to render two columns</p>

CSS

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