The latest in Epic's behind-the-scenes video series detailing the wonders of Unreal Engine 4 is here.

Epic's Francois Antoine (senior FX artist) and Zak Parrish (developer support) discuss how Unreal Engine 4 makes the fireball explosion in the Infiltrator demo possible (hint: a lot of technical stuff otherwise made easier and better looking via the engine).

Here are the some previous videos in this series (water effects & subtle visual effects).

BTW, here's the original Infiltrator demo.