Its xenon gas that once electrically charged ignites to give a brilliant white light. Commonly seen on most BMWs', Mercedes, Acura etc.
And of course on one of the sweetest SLE'* I have ever seen Smellbirds' headlamps are AMAZING, on a couple of occasions this weekend we'd get caught at red lights, bonnie94sse and I would have gotten thru, we'd pull over and keep an eye on a lowered, HID lit Bonneville
Those are 9000k, violet hue. I took some video on the road Wed. night, I just need to get it on a server. People in Wis. must not see HID'* because I got flashed about 7 times on the way home.
I am completely and utterly satisfied with mine, they were everything I expected both in the look it creates and the increased light output. :P