JSFiddle - React, Tailwind, and code Playground

HTML

<div id="img-holder">
    <img  src="http://assets.worldwildlife.org/photos/479/images/priority_species_large/giant-panda-shutterstock_86500690.jpg?1345572346"/>
</div>

CSS

#img-holder{
    position:relative;
    display:inline-block;
    
}


#img-holder:hover:after {
    font-family:verdana;
    content:"Overlay Content";
    color:white;
    background-color:rgba(0,0,0,0.5);
    top:0;
    left:0;
    position:absolute;
    box-sizing:border-box;
    padding-top:150px;
    text-align:center;
    width:100%;
    height:100%;
    -webkit-animation:trans 300ms;
    transition:trans 300ms;
}

@-webkit-keyframes trans {
    from { opacity:0}
    to {opacity: 1} 
}

@keyframes trans {
    from { opacity:0}
    to {opacity: 1} 
}