JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mybutton">Click Here</div>
<div id="mycontainer">
    <div id="sub"></div>
</div>

CSS

#mycontainer {
    color:#FFF;
    background-color: #000;
    width: 12px;
    height: 12px;
    transition: height 100ms, width 100ms ease;
}
#mycontainer.expand {
    width: 400px;
    height: 400px;
}
#sub {
    width:100%; height: 40%; background-color: #555;
}
#mybutton {
}

JavaScript

$("#mybutton").click(function () {
    $("#mycontainer").toggleClass("expand");
});