JSFiddle - React, Tailwind, and code Playground

HTML

<div id="chat">
<div id="mensagens" style="">


  chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>chat
  <br>
  </div>
</div>

CSS

#chat {
  height: 39vh;
  width: 27.5vw;
  display: block;
  overflow: auto;
  position: fixed;
  top: 55vh;
  left: 21vw;
  background-image: url("http://pre11.deviantart.net/b65d/th/pre/i/2005/076/5/e/frame_by_anilestock.jpg");
  background-size: 100% 100%;
  -margin:auto;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
#mensagens
{
  margin-left:30px;
  margin-top:20px;
  width:120px;
  height:139px;
  overflow:auto;
}