JSFiddle - React, Tailwind, and code Playground

HTML

<header>
  Header
</header>

<nav>
  <h2>Navbar</h2>
  <div class="total">
    Essa div possui altura de 100vh
  </div>
</nav>

CSS

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

/* estilos do conteúdo */
header {
  width: 100%;
  background: red;
  height:50px;
}
nav {
  width: 150px;
  height: 150px;
  background: yellow;
  padding: 10px;
}
.total {
  height: 100%;
  width:100%;
  background: #cde;
}