JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parent">
    <div id="child_1">
    </div>
    <div style="clear: both !important"></div>
    <div id="child_2">
    </div>
    <div style="clear: both !important"></div>
</div>

CSS

/*Change the height of this to see the black*/
#parent{width:300px;height:300px;float:left;background:#000;}


#child_1{float:left;background:#0f0;}
#child_2{width:150px;height:300px;float:left;background:#f00;}