JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
    <div id="header"></div>
</div>

CSS

#wrapper{
    height: 1000px;
    width: 100%;
    background-color: rgb(100,100,100);
}
#header{
    height: 300px;
    width: 100%;
    background-color: rgb(255,0,0);
}