JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
  <p>Child</p>
  <div>Child</div>
  <div>Child</div>
  <div>Child</div>
</div>

CSS

.parent :first-child {
  color: red;
}

.parent div:first-child {
  font-size: 20px;
}

.parent div:first-of-type {
  text-decoration: underline;
}


.parent p:first-child {
  text-decoration: line-through;
}

.parent div:nth-child(2) {
  border: 1px black solid;
}

.parent :first-of-type {
  background: yellow;
}