JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" id="btnAdd" value="Add" onclick="AddContent()" />
<div id="cont">
  <div class="sample">
    <div id="thumbs">
      <div id="Minthumbs">
         <span></span>
      </div>
    </div>
  </div>
</div>

JavaScript

AddContent = function() {
    var div = document.getElementById('Minthumbs');
    div.innerHTML += '<div style="color: Red;">content</div><br/>'
}