JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
  <div class="chatbox"></div>
  <div class="wrapper-inner">Content</div>
</div>
<div class="footer"></div>

CSS

body {
  margin: 0;
}

.wrapper {
  background: #95a5a6;
  display: table;
  height: 100vh;
  width: 100%;
}

.wrapper-inner {
  display: table-cell;
  padding-left:300px;
  padding-bottom: 60px;
  vertical-align: middle;
  text-align: center;
}

.chatbox {
  background: #bdc3c7;
  min-height: 100%;
  position: absolute;
  overflow-x: hidden;
  overflow-y: auto;
  width: 300px;
  z-index: 2;
}

.footer {
  background: #2c3e50;
  bottom: 0px;
  height: 60px;
  position: absolute;
  width: 100%;
  z-index: 1;
}