JSFiddle - React, Tailwind, and code Playground

HTML

<div id="blue_box">
    <div id="left">Foo</div>  
    <div id="right">Bar</div> 
</div>

CSS

#left {
  position: relative;
  float: left;
  width: 44%;
  margin: 0;
  padding: 0;
  border-right: 1px solid white;
  height:400px;
}

#right {
  position: relative;
  float: right;
  width: 49%;
  margin: 0;
  padding: 0;
  height:400px;
}

#blue_box {
  background-color:blue;
  border-radius: 10px;
  -moz-border-radius:10px;
  -webkit-border-radius: 10px;
  position: relative;
  width: 45%;
  min-width: 400px;
  max-width: 600px;
  padding: 2%;
  float: right;
  overflow: auto; /*needed so that div stretches with child divs*/
}