JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.2.1/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">



<div class="container-fluid col-md-12">
        <div class="col-sm-6 red">
        column1
        </div>
        <div class="col-sm-6">
            <div class="block blue">
            column2
            </div>
            <div class="block blue">
            column2
            </div>
        </div>
    </div>

CSS

.container-fluid{
  height: 200px; 
  margin-top: 50px;
}

div{
  color: white;
}

.col-sm-6{
  height: 100%;
}


.red, .blue{
  padding: 10px;
}

.red{
  background: tomato;
}

.blue{
  background: blue;
  display: block;
  height: calc(50% - 1px);
}

.blue+.blue{
   margin-top: 2px;
}