<div id="cf">
  <img class="bottom" src="https://d152j5tfobgaot.cloudfront.net/wp-content/uploads/2015/07/blooging.jpg" />
  <img class="top" src="https://d152j5tfobgaot.cloudfront.net/wp-content/uploads/2015/08/blog1.jpg" />
</div>
#cf {
  position:relative;
  height:281px;
  width:450px;
  margin:0 auto;
}

#cf img {
  position:absolute;
  left:0;
  -webkit-transition: opacity 1s ease-in-out;
  -moz-transition: opacity 1s ease-in-out;
  -o-transition: opacity 1s ease-in-out;
  transition: opacity 1s ease-in-out;
}

#cf img.top:hover {
  opacity:0;
}
Run Pen

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.