Zurb TwentyTwenty module is mostly intended to highlight the difference between two images on a Drupal site. You certainly saw those advertising images for skin products, for example. 

They would present half of the face before applying the product and half of the face after applying it. Besides such comparisons, you can use this module for other purposes as well. In this tutorial, you will learn how Zurb TwentyTwenty module works.