Superman is most vulnerable to kryptonite, mineral debris from Krypton transformed into radioactive material by the forces that destroyed the planet. Exposure to kryptonite radiation nullifies Superman's powers and immobilizes him with pain; prolonged exposure will eventually destroy him. The only mineral on Earth that can protect him from Kryptonite is lead, which blocks the radiation. Green kryptonite is the most commonly seen form, but writers introduced other forms over the years, such as red, gold, blue, and black, each with its own effect.