In the new "Pirates of the Caribbean" film there were shots when Johnny Depp needed to look much younger. He needed to go from his real age of 53 down to around 25. This wasn't going to be possible using make-up so the directors needed to find another way.
This is where vfx techniques come into practice. Special effects are no longer limited to explosions and monsters. Lola VFX was the company behind this transformation. It took 15 of their artists a year to complete the 20 - 25 altered shots of Depp.
(Image - Pirates of the Caribbean: Dead Men Tell No Tales)