JSFiddle - React, Tailwind, and code Playground

HTML

<nav id="nav">
  <ul>
    <li><a href="#">Item21</a>
    <ul>
      <li><a href="#">Sub1</a>
      <li><a href="#">Sub1</a>
        <li><a href="#">Sub1</a>
    	 <ul>
    		<li><a href="#">Sub2</a></li>
    		<li><a href="#">Sub2</a></li>
    		<li><a href="#">Sub2</a></li>
     	 </ul>
    
        </li>
    </ul>
    </li>
  </ul>
 
</nav>

CSS

#nav {
	height: auto;
	width: auto;
}
#nav ul {
	margin: 0px;
	padding: 0px;
	list-style-type: none;
}
#nav ul li {
	float: left;
	position: relative;
}
#nav ul li a {
	line-height: 30px;
	text-decoration: none;
	text-align: center;
	display: block;
	width: 100px;
	height: 30px;
	border: thin solid #999;
	color: #FFF;
	background-color: #0CF;
	-webkit-transition: all 1s;
	-moz-transition: all 1s;
	-ms-transition: all 1s;
	-o-transition: all 1s;
	transition: all 1s;
}
#nav ul li a:hover {
	background-color: #0C3;
}
#nav ul li ul {
	position: absolute;
	visibility: hidden;
	-webkit-transition: all 1s linear 0s;
	-moz-transition: all 1s linear 0s;
	-ms-transition: all 1s linear 0s;
	-o-transition: all 1s linear 0s;
	transition: all 1s linear 0s;
	overflow: hidden;
	height: 0px;
}
#nav ul li:hover ul {
	height: 100px;
	visibility: visible;
	overflow: visible;
}
#nav ul li ul li {
	-ms-transition: all 1s;
	-o-transition: all 1s;
}
#nav ul li ul li a {
	background-color: #FF881A;
	-webkit-transition: all 1s;
	-moz-transition: all 1s;
	-ms-transition: all 1s;
	-o-transition: all 1s;
	transition: all 1s;
}
#nav ul li ul li a:hover {
	background-color: #C30;
}
#nav ul li ul li ul {
	position: absolute;
	left: 102px;
	top: 0px;
	display: none;
	-webkit-transition: all 1s ease 0s;
	-moz-transition: all 1s ease 0s;
	-ms-transition: all 1s ease 0s;
	-o-transition: all 1s ease 0s;
	transition: all 1s ease 0s;
	overflow: hidden;
	visibility: hidden;
	width: 0px;
}
#nav ul li ul li ul li {
	float: left;
	position: relative;
}
#nav ul li ul li:hover ul {
	width: 104px;
	display: block;
	overflow: visible;
	visibility: visible;
}