JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parent" class="parent">
    <div id="child" class="child">
    </div>
</div>

CSS

.parent{
    border-style: solid;
    border-color: green;
    border-bottom: solid 10px;
    background:grey;
    width: 300px;
    height: 300px;
    padding: 10px;
}
.child{
    border: 20px solid;
    background: aqua;
    border-color: green;
    height: 50px;
    margin: 10px;
}