JSFiddle - React, Tailwind, and code Playground

HTML

<iframe width="420" height="315" src="//www.youtube.com/embed/1sIWez9HAbA" frameborder="0" allowfullscreen></iframe>

<div>Click the thumbnail</div>

CSS

div {float:left;margin:20px;}
iframe {display:none;}
img {float:left;width:120px;height:90px;cursor:pointer;}

JavaScript

var iframe           = $('iframe:first');
var iframe_src       = iframe.attr('src');
var youtube_video_id = iframe_src.match(/youtube\.com.*(\?v=|\/embed\/)(.{11})/).pop();

var video_thumbnail = $('<img src="//img.youtube.com/vi/'+youtube_video_id+'/0.jpg">');
$('body').append(video_thumbnail);

$('img:first').click(function() {
    $('iframe:first').fadeToggle('400');
});