JSFiddle - React, Tailwind, and code Playground

HTML

<aside>
  <ul>
    <li>menu</li>
    <li>menu</li>
    <li>menu</li>
    <li>menu</li>
    <li>menu</li>
    <li>menu</li>
    <li>menu</li>
    <li>menu</li>
    <li>menu</li>
  </ul>
</aside>
<article>
  conteudo
</article>

CSS

body, html {
  margin:0; padding:0;
}
* {
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}

/* estilos do conteĂşdo */
aside, article {
  display:inline-block;
  float:left;
}
aside {
  height: 100vh;
  background:#cde;
  width:20%;
  overflow-y: auto;
}
ul {
  list-style:none;
  padding:0; margin:0;
}
ul li {
  padding: 20px;
  cursor:pointer;
}
ul li:hover {
  background: #f0f;
}
article {
  min-height: 100vh;
  background: white;
  padding: 20px;
  width: 80%;
}