Untitled

<!DOCTYPE html>
<html>
<head>
<style>
    .box > div > div > div > div{
        background: #ff0000;
        }
</style>
</head>
<body>
<div class="box">
   <div>
       The first paragraph.
       <div>
           The second paragraph.
           <div>
               The third paragraph.
               <div>
                   The fourth paragraph. (tip)
               </div>
           </div>
       </div>
   </div>
</div>
</body>
</html>