JSFiddle - React, Tailwind, and code Playground

HTML

<div id=abox>a
    <div id=bbox>b
    </div>
</div>

CSS

#abox {
    outline: 1px red solid;
    position: absolute;
    top: 10px;
    left: 10px;
    width: 100px;
    height: 100px;
}
#bbox {
    outline: 1px green solid;
    position: absolute;
    top: 40px;
    left: 90px;
    width: 40px;
    height: 40px;
}