Nested lists

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Nested lists</title>
</head>

<body>
    <ol type="I">
        <li>List item 1
            <ol type="a">
                <li>Nested item 1.1</li>
                <li>Nested item 1.2</li>
            </ol>
        </li>
        <li>List item 2
            <ol>
                <li>Nested item 2.1</li>
                <li>Nested item 2.2
                    <!--not default-->
                    <ul type="circle">
                        <li>Nested item 2.2.1</li>
                        <li>Nested item 2.2.2</li>
                        <li>Nested item 2.2.3</li>
                    </ul>
                </li>
                <li>Nested item 2.3</li>
            </ol>
        </li>
        <li>List item 3
            <!--default-->
            <ul>
                <li>Nested item 3.1</li>
                <li>Nested item 3.2</li>
                <li>Nested item 3.3</li>
            </ul>
        </li>
    </ol>
</body>

</html>