JSFiddle - React, Tailwind, and code Playground

HTML

<video class="thumb" autoplay loop onclick="expandVid(this)">
    <source src="http://zippy.gfycat.com/PolishedBelatedAltiplanochinchillamouse.webm" type="video/webm" />
    <img src="." alt="Your browser does not support HTML5 video tag" />
</video>

CSS

video.thumb {
    max-width: 200px;
    max-height: 200px;
}

JavaScript

function expandVid(elem) {
    if (elem.className) { // Is thumb
        elem.className = ''; // Expand it
    } else if (!elem.hasAttribute('controls')) { // Is not thumb and has no controls
        elem.className = 'thumb'; // Make it thumb
    }
}