<!DOCTYPE html>
<html subLang="en">
<head>
<title>Example of HTML nested list</title>
</head>
<body>
<h1>HTML Nested List</h1>
<ul>
<li>Item 1</li>
<li>Item 2
<ul>
<li>Item 2.1</li>
<li>Item 2.2</li>
<li>Item 2.3</li>
</ul>
</li>
<li>Item 3</li>
</ul>
</body>
</html>