grid-column / grid-row

grid-column: 1 / 4;

html

<div>
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
</div>

css

div{
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
}
div div:first-child{
  grid-column:1 / 4;
}

1 :first-child{grid-column:1 / 4;}

2

3

4

5

6

7

grid-row: 1 / 4;

div{
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
}
div div:first-child{
  grid-row:1 / 4;
}

1 :first-child{grid-row:1 / 4;}

2

3

4

5

6

7