JSFiddle - React, Tailwind, and code Playground

HTML

<div id="c">
    <div id="r"></div>
    <div id="o"></div>
</div>

CSS

#c {
    position:relative;
    width:50px; height:20px;
}
#r {
    background:url('http://www.dnolan.com/code/js/rollover/rollover.gif');
    cursor:pointer;
    opacity:1;
    width:50px; height:20px;
    position:absolute; z-index:2;
    transition: all ease 2s;
    -moz-transition: all ease 2s;
    -webkit-transition: all ease 2s;
}
#r:hover {
    opacity:0;
    transition: all ease 2s;
    -moz-transition: all ease 2s;
    -webkit-transition: all ease 2s;
}
#o {
    background:url('http://www.dnolan.com/code/js/rollover/rollover_o.gif');
    width:50px; height:20px;
    position:absolute; z-index:1;
}