JSFiddle - React, Tailwind, and code Playground

HTML

<div id="con">
    <div id="big">
        <div id="small"></div>
    </div>
</div>

CSS

#big {
    width:200px;
    height:200px;
    background:red;
    position:relative;
}
#small {
    position:absolute;
    width:50px;
    height:50px;
    margin-left:-25px;
    margin-top:-25px;
    left:50%;
    top:50%;
    background:blue;
}