The website you give as an example uses CSS Transitions to make some of their images grow and shrink. You can learn more about CSS Transitions at https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Transitions/Using_CSS_transitions
Below is a simple example using JQuery. When you click on the Google logo it will grow and when you click on it again it will shrink.
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<style>
.box img {
transition: width .4s,margin .4s,max-width .4s;
transition-property: width, margin, max-width;
transition-duration: 0.4s, 0.4s, 0.4s;
transition-timing-function: ease, ease, ease;
transition-delay: 0s, 0s, 0s;
}
.box img.clicked{
width: 500px;
}
</style>
<script>
$(function(){
$('.box img').on('click', function() {
$(this).toggleClass('clicked');
});
});
</script>
</head>
<body>
<div class="box">
<img src="https://www.google.com/images/srpr/logo11w.png" width="100" />
</div>
</body>
</html>