JSFiddle - React, Tailwind, and code Playground

HTML

<div id='a'>
    <div id='b'></div>
</div>

CSS

#a, html, body{
    height: 100%;
}
#a {
    width: 300px;
    background-color: #dde;
    border: 1px solid #99c;
    position:relative;
    overflow: hidden
}

#b {
    width: 50px; 
    height: 50px;
    background-color: #99c;
    border: 1px solid #54a;
    position: absolute;
    bottom: -25px;
    left: 125px;
}