<!DOCTYPE html>
<div style="width: 100px; height: 100px; background: green; position: relative">
  <div style="width: 50px; height: 50px; background: blue; position: absolute; top: 20px; left: 20px"></div>
  <div style="width: 50px; height: 50px; background: magenta; position: absolute; top: 0; left: 0"></div>
</div>
