JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent" style="height:auto;">
    <div style="float:left;height:500px;background:#00FF00;">
        inner div 1
    </div>
    <div style="float:right;height:500px;background:#0000FF;">
        inner div 2
    </div>
</div>

CSS

.parent{
    border: solid 2px #333;
    background: #FF0000;
    min-height: 300px;
}