JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container"><div class="box"></div></div>

CSS

body, html{
    display:table;
    height:100%;
    width:100%;
}
.container{
    display:table-cell;
    vertical-align:middle;
}
.container .box{
    width:100px;
    height:100px;
    background:red;
    margin:0 auto;
    
}