JSFiddle - React, Tailwind, and code Playground

HTML

<div style="height: 100%">
    <div class="title">Title</div>
    <div class="cont">Content</div>
</div>

CSS

html, body {
    height:100%;
    width:100%;
    margin:0;
    padding:0
}
.title {
    height:100px;
    border:1px solid red
}
.cont {
    height:calc(100% - 100px);
    border:1px solid green
}