display grid

                                    .parent{
  display: grid;
  grid-template-columns: repeat(3, 250px);
  /*
    instead of writing 250px 250px 250px 3 times, we use repeat(number of columns, width) function
  */
  grid-template-rows: repeat(3, 400px);
}
.parent .child-1{
  grid-column: 2 / 4; /* Start at column 2 and end at column 3, 4 not counted [not inlcuded]*/
  grid-row: span 2; /* take only 2 rows. can be written also as [grid-row: 1 / 3]*/
}
.parent .child-2{
  grid-column: span 3;
  grid-row: 1 / 3; /* 2 rows */
}
/*
  ShortHand
  grid-column: grid-column-start grid-column-end
  grid-row: grid-row-start grid-row-end
  Example: 
    *grid-column: 2 / 8; start at 2 and end at 8-1 = 7
    => grid-column-start = 2, grid-column-end = 7
*/

                                    .container {
  display: grid | inline-grid;
}

                                    .item-a {
  grid-area: header;
}
.item-b {
  grid-area: main;
}
.item-c {
  grid-area: sidebar;
}
.item-d {
  grid-area: footer;
}

.container {
  display: grid;
  grid-template-columns: 50px 50px 50px 50px;
  grid-template-rows: auto;
  grid-template-areas: 
    "header header header header"
    "main main . sidebar"
    "footer footer footer footer";
}

                                    grid-template-columns: auto auto auto;

                                    .item-a {
  grid-column: 1;
  grid-row: 1 / 3;
}
.item-e {
  grid-column: 5;
  grid-row: 1 / 3;
}