Create Grids within Grids

<style>
  .container {
    font-size: 1.5em;
    min-height: 300px;
    width: 100%;
    background: LightGray;
    display: grid;
    grid-template-columns: auto 1fr;
    grid-template-rows: auto 1fr auto;
    grid-gap: 10px;
    grid-template-areas:
      "advert header"
      "advert content"
      "advert footer";
  }
  .item1 {
    background: LightSkyBlue;
    grid-area: header;
  }

  .item2 {
    background: LightSalmon;
    grid-area: advert;
  }

  .item3 {
    background: PaleTurquoise;
    grid-area: content;
    /* Only change code below this line */
    display: grid;
    grid-template-columns: auto 1fr;

    /* Only change code above this line */
  }

  .item4 {
    background: lightpink;
    grid-area: footer;
  }

  .itemOne {
    background: PaleGreen;
  }

  .itemTwo {
    background: BlanchedAlmond;
  }

</style>

<div class="container">
  <div class="item1">header</div>
  <div class="item2">advert</div>
  <div class="item3">
    <div class="itemOne">paragraph1</div>
    <div class="itemTwo">paragraph2</div>
  </div>
  <div class="item4">footer</div>
</div>