<div class="row">
  <div class="col-sm-9">
    Columna nivel 1
    <div class="row">
      <div class="col-xs-8 col-sm-6">
        Columna nivel 2
      </div>
      <div class="col-xs-4 col-sm-6">
        Columna nivel 2
      </div>
    </div>
  </div>
</div>

External CSS

  1. //maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.