JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
  <div class="side">
    <h2 class="text">Side</h2>
  </div>
  <div class="container">
    <div class="header">
      <h2 class="text">Header</h2>
    </div>
    <div class="content">
      <h2 class="text">Content</h2>
    </div>
  </div>
</div>
dasd

CSS

.parent {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  height: 100vh;
  border: 20px solid black;
  display: flex;
  flex-direction: row;
}

.header {
  height: 30%;
  background: cornflowerblue;
}

.side {
  width: 30%;
  height: 100%;
  background: rgb(219, 133, 133);
}

.content {
  height: 70%;
  background: rgb(115, 202, 180);
}

.text {
  display: flex;
  flex-direction: row;
  justify-content: center;
  align-items: center;
  height: 190px;
  color: #fff;
}

.container {
  display: flex;
  flex-direction: column;
  width: 70%;
  height: 100%;
}