JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div class="big"></div>
    <div>
        <ul>
            <li>Element #1</li>
            <li>Element #2</li>
            <li>Element #3</li>
            <li>Element #4</li>
            <li>Element #5</li>
        </ul>
    </div>
</div>

CSS

#container ul {
    list-style: none;
    margin: 0;
    overflow-y: scroll;
    position: absolute;
    top: 31px;
    left: 0;
    right: 0;
    bottom: 0;
}

#container {
    height: auto;
    display: -moz-box;
    display: -webkit-box;
    display: box;
}

#container div{
    position: relative;
    height: 100%;
    width: 200px;
}

#container div.big{
    height: 500px;
}