JSFiddle - React, Tailwind, and code Playground

HTML

<div id="a">
    <div id="b">
        <div id="content"></div>
    </div>
</div>

CSS

html, body, #a {
    margin: 0;
    padding: 0;
    height: 100%;
    width: 100%;
}

#a {
    display: table;
}

#b {
    display: table-cell;
    margin: 0;
    padding: 0;

    text-align: center;
    vertical-align: middle;
}

#content {
    border: 5px solid red;
    width: 100px;
    height: 100px;
    margin: auto;
}