JSFiddle - React, Tailwind, and code Playground

HTML

<div class="navigation">
    <div class="item">A.</div>
    <div class="item subnavigation">
        Scroll content<br />
        Lorem ipsum...LALALALA<br />
        Just more stuff<br />
        And more<br />
        And a bit more...
    </div>
    <div class="item">B.</div>
</div>

CSS

.navigation{
    padding: 5px;
    float: left;
}

.item
{
    float: left;
    margin: -5px 5px;
}

.subnavigation{
    padding: 5px;
    border:1px dashed #fff;
    border-top-width:0px;
    border-bottom-width:0px;
    overflow: auto;
    background: #666;
}