<div class="grid">grid
  <div class="subgrid">subgrid
    <div class="subitem">subitem</div>
  </div>
</div>
body {
  font-size: 30px;
  text-align: center;
  font-family: 'Google Sans', sans-serif; 
}
.grid {
  padding: 10px;
  width: min-content;
  display: grid;
  grid-template-columns: repeat(8, 50px);
  grid-template-rows: repeat(3, minmax(30px, auto));
  border: 4px solid royalblue;
}
.subgrid {
  padding: 10px;
  border: 4px solid gold;
  display: grid;
  grid-column: 2 / 8;
  grid-row: 2 / 4;
  grid-template-columns: subgrid;
  grid-template-rows: subgrid;
}

.subitem {
  padding: 10px;
  border: 4px solid rebeccapurple;
  grid-column: 4 / 7;
  grid-row: 1 / 3;
}

External CSS

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External JavaScript

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