<div class="grid">
  <div class="box">A</div>
  <div class="box">B</div>
  <div class="box">C</div>
  <div class="box">D</div>
  <div class="box">E</div>
  <div class="box">F</div>
  <div class="box">G</div>
  <div class="box">H</div>
  <div class="box">I</div>
</div>
.grid {
  display: grid;
  grid-gap: 10px;
  grid-template-columns: 1fr 1fr 1fr;
  grid-template-rows: 1fr 1fr 1fr;
}

/* Styling */
.box {
  background: #ccc;
  color: #ggg;
  text-align: center;
  padding: 10px;
  border-radius: 3px;
}

body {
  font-family: -apple-system, sans-serif;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.