What are the functional groups found in caffeine? Based on organic chemistry?

Answer 1

If you want to look at the structure of caffeine:
http://images.google.com/images?hl=en&q=caffeine&btnG=Search+Images&gbv=2

Basically it's a fused bicylclic system with ketones, heterocylclic N-methyls, and heterocyclic nitrogens.