<!DOCTYPE html>
<!--
 | "overflow" property affects the clipping of all of the element's content
 | except any descendant elements whose containing block is the viewport or
 | an ancestor of the element.
 |   https://www.w3.org/TR/CSS21/visufx.html#overflow
 -->
<html>
<head>
  <style>
    .outer {
      background-color: rgba(63, 81, 181, 0.9);
      height: 100px;
      margin-bottom: 100px;
      overflow: hidden;
      width: 100px;
    }
    .absolutely-positioned {
      position: absolute;
    }
    .inner {
      background-color: #2196f3;
      height: 100px;
      left: 50px;
      position: absolute;
      top: 50px;
      width: 100px;
      z-index: -1;
    }
  </style>
</head>
<body>
  <div class="outer">
    <div class="inner"></div>
  </div>
  <div class="absolutely-positioned outer">
    <div class="inner"></div>
  </div>
</body>
</html>