Kryptonite is a mineral from Clark's home planet Krypton. According to some comics, kryptonite was created when the core of Krypton became radioactive just before it exploded, but in Smallville it was also placed in Asia, presumably da Clark's ancestor 500 years ago, suggesting that it might be a natural occurring radioactive element from Krypton. The known variations of kryptonite affect Clark in different ways. Fortunately, for external exposure, Clark can protect himself from kryptonite using lead and removal of the substance reverses the effects almost immediately. If it gets into his system,...