JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div class="columnA"></div>
    <div class="columnB"></div>
</div>

CSS

.columnA{height:200px; width:50px; background-color:#FF0000; float:left;}
.columnB{height:300px; width:50px; background-color:#00FF00;}
.parent{height:300px; width:100px;}