<!DOCTYPE html>
<style>
#container {
  position: absolute;
  z-index: 0;
  left: 50px;
  top: 50px;
}

.child {
  position: absolute;
  width: 40px;
  height: 40px;
  background-color: red;
}

.embiggen {
  width: 50px;
  height: 50px;
  background-color: green;
}
</style>
<div style="width:200px; height:200px; background-color: lightblue"></div>
<div id="container">
  <span class="child embiggen"></span>
</div>