JSFiddle - React, Tailwind, and code Playground

HTML

<div>
<p></p>
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah<br />
blah
</div>

CSS

div
{
    margin-top: 100px;
    width: 100%;
    height: 200px;
    background: #F00;
    overflow-y: scroll;
}

p
{
    width: 100%;
    height: 40px;
    position: fixed;
    background: #000;
    opacity: 0.5;
    filter: opacity(alpha=50);
}