JSFiddle - React, Tailwind, and code Playground

HTML

<h2>Tooltip</h2>
<p>Move the mouse over the text below:</p>

<div class="tooltip" tooltip="This is a tooltip">
  Hover over me
</div>

CSS

body {
  padding: 50px;
}

.tooltip {
  position: relative;
  display: inline-block;
  border-bottom: 1px dotted black;
  z-index: 2;
  cursor: pointer;
}

[tooltip]::before,
[tooltip]::after {
  position: absolute;
  bottom: 125%;
  left: 50%;
  visibility: hidden;
  opacity: 0;
  pointer-events: none;
  transition: opacity 1s;
}

[tooltip]::before {
  content: attr(tooltip);

  /* Cosmetics */
  color: #fff;
  background-color: #555;
  width: 120px;
  text-align: center;
  padding: 5px 0;
  margin-bottom: 5px;
  margin-left: -60px;
  border-radius: 6px;
  opacity: 0;
}

[tooltip]::after {
  content: "";

  /* This creates the indicators */
  margin-left: -5px;
  border-top: 5px solid #555;
  border-right: 5px solid transparent;
  border-left: 5px solid transparent;
}

[tooltip]:hover::before,
[tooltip]:hover::after {
  visibility: visible;
  opacity: 1;
}