JSFiddle - React, Tailwind, and code Playground

HTML

<div id="Container">
    <div id="TheElement"></div>
</div>

CSS

#Container {
    width: 500px;
    height: 600px;
    position: relative;
    background: #ccc
}

#TheElement {
    width: 500px;
    height: 100px;
    background-color: #000000;
    position: absolute;
    bottom: 0;
    left: 0;
}