JSFiddle - React, Tailwind, and code Playground

HTML

<div id="summary">Sample</div>
<div id="detail">Detail of this summary</div>

CSS

#summary:hover + #detail, #detail:hover {
  display: block;
}
#detail {
  display: none;
}


/* Colors */

#summary {
  background-color: #ddd;
}
#detail {
  background-color: #ccc;   
}