JSFiddle - React, Tailwind, and code Playground

HTML

<div id="outer">
    <div id="inner">
        content
    </div>
</div>

CSS

#outer::before {
    display: block;
    content: "";
    height: 10%;
}
#outer::after {
    display: block;
    content: "";
    height: 10%;
}
#inner {
    height: 80%;
    margin-left: 10%;
    margin-right: 10%;
}

html, body { height: 100%; }
#outer {
    background-color: purple;
    width: 50%;
    height: 50%;
    box-sizing: border-box;
}
#inner {
    background-color: yellow;
}