JSFiddle - React, Tailwind, and code Playground

HTML

<div class="nav-con">
  <nav role='navigation' id="nav">
    <ul>
      <li id="linked"><a href="#">Home</a></li>
      <li><a href="#">About</a>
          <ul class="dropdown">
            <li>Link 1.</li>
            <li>Link 2.</li>
            <li>Link 3</li>
          </ul>  
      </li>
      <li><a href="#">Clients</a>
          <ul class="dropdown">
            <li>Link 1.</li>
            <li>Link 2.</li>
            <li>Link 3</li>
          </ul>  
      </li>
      <li><a href="#">Contact Us</a>
          <ul class="dropdown">
            <li>Link 1.</li>
            <li>Link 2.</li>
            <li>Link 3</li>
          </ul>  
      </li>
    </ul>
	</nav>

CSS

.clearfix:before,  
.clearfix:after {  
    content: " ";  
    display: table;  
}  
.clearfix:after {  
    clear: both;  
}  
.clearfix {  
    *zoom: 1;  
}  

nav {
  width: 100%;
  height: 60px;
  background-color:black;
  border-bottom: #ffd600 solid 10px; 
  margin: 0 auto;
}

nav ul {
  position:inheirt;
}

nav ul li {
	transition: all .6s ease-in-out;
  -moz-transition: all .6s ease-in-out;
  -o-transition: all .6s ease-in-out;
  -webkit-transition: all .6s ease-in-out;
  width: 80px;
  height:60px;
  margin-left:10px;
  display:;
  float: left;
  line-height: 60px;
  text-align:center;
  list-style:none;
  position:inherit;
  color: white;
  text-decoration:none;
}

 nav ul li:hover {
  width: 80px;
  -moz-transition: all .6s ease-in-out;
  -o-transition: all .6s ease-in-out;
  -webkit-transition: all .6s ease-in-out;
  height:60px;
  margin-left:10px;
  background-color:#ffd600;
  float: left;
  line-height: 60px;
  text-align:center;
  list-style:none;
  position:inherit;
  color: white;
  text-decoration:none;
}

nav ul li a {
  color: white;
  text-decoration:none;
}

html {
  background-color: #f2f2f2;
}

#dropdown {
	width:100%;
  height:200px;
  opacity: 0.8;
  background-color:black;
	display:none;
}


.dropdown {
  margin-top:10px;
  
}
.dropdown li {
  width: 300px;
  background-color: #ffd600;
}

nav ul ul {
	opacity: 0;
  transition: all .6s ease-in-out;
  -moz-transition: all .6s ease-in-out;
  -o-transition: all .6s ease-in-out;
  -webkit-transition: all .6s ease-in
}

nav ul li:hover > ul {
		opacity: 0.8;
    transition: all .6s ease-in-out;
    -moz-transition: all .6s ease-in-out;
    -o-transition: all .6s ease-in-out;
    -webkit-transition: all .6s ease-in-out;
	}

nav ul ul li {
  opacity: 1.0 !important;
}

nav ul ul li:hover {
  width: 350px !important;
}