JSFiddle - React, Tailwind, and code Playground

HTML

<div>
<h1>Header</h1>
    <div class="container">
        <div class="content"></div>
    </div>
</div>

CSS

.container {
    height: 300px;
    position: relative;
    overflow-y:scroll;
}
.content {
    height:1000px;
}
h1 {
    position: relative;
    top:0px;
    left:0px;
    margin: 0;
    width: 100%;
    background: black;
    color: white;
}