JSFiddle - React, Tailwind, and code Playground

HTML

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

SCSS

.parent {
    width: 50px;
    height: 50px;
    background-color: red;
}
.child {
    width: 30px;
    height: 30px;
    background-color: green;
    .parent & {
        background-color: black; 
    }
}