JSFiddle - React, Tailwind, and code Playground

HTML

<br /> <br /> <br /> <br />

    <div id="blue">
        <div id="red"></div>
    </div>

</div>

<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />
<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />
<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />
<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />
<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />
<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />

CSS

#blue {
    height:300px;
    width:200px;
    background:blue;
}

#red {
    height:50px;
    width:200px;
    position:fixed;
    background:red;
}