You know, the powers that be here at RIU, they knew that they would get a lot of questions like this. In their INFINITE wisdom, they created *the clouds part, light shines, and a band of angels begins to play IRON MAN* the GrowFAQ
GROWFAQ
lol, all joking aside, that link should take you right to what you're looking for in the GrowFAQ. They explain everything, even show you a few DIY set ups. Good luck