JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="subject">
        contents...
    </div>
</div>

CSS

#container {
    position: absolute;
    margin:0px;
    padding:0px;
    width: 300px;
    height: 100px;
    background: #aaa;
}

#subject {
    position: absolute;
    top: 0px;
    bottom: 0px;
    left: 0px;
    right: 0px;
    padding: 10px 20px;
    background: #aaf;
}