I've seen python scripts by Face-Off, Templargfx, and  I think bagginsbill, that all deal with this topic, but I have no idea how it's accomplished?

What's the least you should know about it's definition before you could tell someone you understand what it is?

What are the basic steps needed to recreate this in the Material Room?

Has anyone else noticed it works better on Medium-Dark, and Medium complexions, than on very Fair skin, by a long shot, why?

Why doesn't Poser come with this out of the box?  Are there any prospects to see this in Poser 7, or will it remain up to the Python Masters?