react-css-transition.css

.example-component {
  width: 100px;
  height: 100px;
  background-color: red;
  -webkit-transition: 0.5s;
  -moz-transition: 0.5s;
  -o-transition: 0.5s;
  transition: 0.5s;
  opacity: 0;
  visibility: hidden; 
}
.example-component.show {
  opacity: 1;
  visibility: visible; 
}