JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="box red"></div>
    <div class="box blue"></div>
</div>

CSS

* {
    padding: 0;
    margin: 0;
}
html,body {
    height: 100%;
}
.container {
    width: 100%;
    height: 100%;
    background-color: yellow;
}

.box {
  width: 40%;
  height: 90%;
  margin: 5%;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  float: left;
}

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