<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
</head>
<body>
<h2>A nested HTML list</h2>
<p>A nested list contains a list inside a list.</p>
<ul>
<li>Copybooks</li>
<li>
Books
<ul>
<li>Detective books</li>
<li>Roman books</li>
<li>Fairy tale books</li>
</ul>
</li>
</ul>
</body>
</html>