JSFiddle - React, Tailwind, and code Playground

HTML

<img src="http://festivalsvilupposostenibile.it/layout/asvis/img/festival18/te1.png" id="img1" ></img>
<img src="http://festivalsvilupposostenibile.it/layout/asvis/img/festival18/te2.png" id="img2" style="display:none;"></img>
<br>
<input type="button"value="Start" id="start"></input>

JavaScript

$("#start").click(function(){
    $("#img1").fadeOut(3000, function() {
        $("#img2").fadeIn(3000);
  });
});