<!DOCTYPE html>
<html>
  <head>
    <style type="text/css">
      .container {
        width: 60px;
        height: 60px;
      }
      .background {
        width: 50px;
        height: 50px;
        background-color: green;
      }
      .content {
        width: 25px;
        height: 25px;
        background-color: blue;
      }
    </style>
  </head>

  <body>
    <div class="container">
      <div class="background">
        <div class="content"></div>
    </div>
    </div>
  </body>
</html>