JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<body>
  <header>
    <nav>nav</nav>
  </header>
  <aside>aside</aside>
  <main>main</main>
</body>
</html>

CSS

body {
  display: grid;
  grid-template-areas: 
	"header header"
	"aside main";
	grid-template-columns: 275px 1fr;
	grid-template-rows: 1fr 1fr;
}

header {
  grid-area: header;
  border: solid 1px black;
}

header > nav {

  border: solid 1px blue;
}

aside {
  grid-area: aside;
}

main {
  grid-area: main;
}