The Unreal Engine. Various iterations of this technological power house have been the basis of gaming behemoths such as Deus Ex, Bioshock, Killing Floor, the Batman Arkham series and Mass Effect. And now you can get to grips with the engine itself through a series of tutorials from Epic.
The first in the series, embedded above, looks at how the engine handles level streaming. For those of you like myself who aren't developers, that's basically the technology that allows larger environments to be broken up into smaller chunks so that players may move through them seamlessly with few to no loading screens. A very useful tutorial indeed.
Epic intends to release more of these tutorials (yay!) but have not released a broadcast schedule. You can see future episodes first via the Epic Twitch channel.