#container {

  height: 200px;

  border: 2px solid purple;

  display: grid;

  grid-template: repeat(3, 1fr) / repeat(3, 1fr);

}

​

#container > div {

  border: 1px solid grey;

  background-clip: content-box;

  background-color: greenyellow;

  padding: 4px;

  font-size: 20px;

}

​

#container > div:nth-child(1) {

  grid-column-start: 1;

  grid-column-end: 4;

  grid-row-start: 1;

  grid-row-end: 3;

  /*   z-index: 2; */

}

​

#container > div:nth-child(2) {

  grid-column-start: 1;

  grid-row-start: 2;

  grid-row-end: 4;

}

​