JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
<div id="box">

</div>
<div id="popup">

</div>
</div>

CSS

#box {
  height:200px;
  width:200px;
  position:absolute;
  top:0;
  left:50px;
  background: green;
  
}
#popup {
  height:100px;
  width:100px;
  position: absolute;
  z-index:99;
  top:0
  left:75px;
  background: red;
  display: none;
}

JavaScript

$('#box,#popup').mouseenter(function(){
  $('#popup').show();
});
$('#box,#popup').mouseleave(function(){
  $('#popup').hide();
});