<div>1</div>
<div class="o-hide">2</div>
<div>3</div>

div {
  padding: 60px;
  width: 60px;
  font-size: 3em;
  background: pink;
  text-align: center;
  margin: 1%;
  display: inline-block;
  float: left;
  cursor: pointer;
  font-family: 'Lato';
}

.o-hide {
  opacity: 0;
  transition: all ease 0.8s;
}

.o-hide:hover {
  opacity: 1;
}