JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tree" style="width:256px; height:256px;">
    <div>
        <ul>
            <li>
                <div><span>Lorem ipsum</span>
                </div>
            </li>
            <li>
                <div><span>Lorem ipsum</span>
                </div>
            </li>
            <li class="expanded">
                <div> <span>Lorem ipsum</span>
                </div>
                <ul>
                    <li>
                        <div> <span>Lorem ipsum dolor sit amet, consectetur adipisicing elit</span>

                        </div>
                    </li>
                </ul>
            </li>
        </ul>
    </div>
</div>
</div>

CSS

.tree {
    position:relative;
    display: block;
    overflow: auto;
    border: 1px solid #8B9097;
    background-color: #fff;
    margin-left:200px;
    /*! margin-left: just for testing */
}
.tree > div {
    display:block;
    position:absolute;
    min-width:100%;
}
.tree * {
    white-space: nowrap;
}
.tree ul {
    margin:0;
    list-style-type: none;
    padding-left: 20px;
}
.tree li > div {
    position:relative;
    margin-left:-100000px;
    padding-left:100000px;
    border: 1px solid transparent;
    display:block;
}
.tree li div:hover {
    background-color: #B6BABF;
    color: #fff;
}
.tree li.collapsed > ul {
    display:none;
}

.tree li.expanded > ul {
    display:inherit;
}