JSFiddle - React, Tailwind, and code Playground

HTML

<div class="root">
        Top
        <div class="footer">Bottom</div>
    </div>

CSS

.root { 
    background-color: red;
    position: absolute;
    height: auto;
    bottom: 0;
    top: 0;
    left: 0;
    right: 0;
    margin: 25px;
    border: 0;
    border-radius: 7px;
    overflow: hidden;
}

.footer {
    background-color: green;
    position: fixed;
    left: 0;
    bottom: 0;
    width: 100%;
    height: 100px;
}