.div1 {
  position: relative;
  top: 0px;
  left: 0px;
  width: 100px;
  height: 100px;
  background-color: red;
  
  &:before {
    position: absolute;
    top: 10px;
    left: 10px;
    content: '';
    width: 100px;
    height: 100px;
    background-color: green;
  }
  
  &:after {
    position: absolute;
    top: 20px;
    left: 20px;
    content: '';
    width: 100px;
    height: 100px;
    background-color: blue;
  }
}