JSFiddle - React, Tailwind, and code Playground

HTML

<nav>
    <ul>
        <li>One</li>
        <li>
            Two
            <ul>
                <li>Child 1</li>
                <li>Child 2</li>
            </ul>
        </li>
        <li>Three</li>
    </ul>
</nav>

CSS

nav > ul {
    list-style: none;
}
nav > ul > li {
    float: left;
    margin-right: 10px;
}
nav > ul > li:hover ul {
    display: block;
}
nav > ul > li > ul {
    display: none;
}