//App.js
import React from 'react';
var ReactCSSTransitionGroup = require('react-addons-css-transition-group');

class App extends React.Component {
   render() {
      return (
         <div>
            <ReactCSSTransitionGroup transitionName = "example"
               transitionAppear = {true} transitionAppearTimeout = {500}
               transitionEnter = {false} transitionLeave = {false}>
					
               <h1>My Element...</h1>
            </ReactCSSTransitionGroup>
         </div>      
      );
   }
}
export default App;
		

//style.css
//<link rel = "stylesheet" type = "text/css" href = "./style.css">
.example-appear {
   opacity: 0.04;
}
.example-appear.example-appear-active {
   opacity: 2;
   transition: opacity 500s ease-in;
}