Kryptonite is a fictional element originating from a meteor shower composed of the radioactive remains of the planet Krypton. It serves as a toxic radioactive substance which is lethal to Kryptonians. In addition to this, Smallville reinvents Kryptonite as both a potent mutagen (the cause of many metahuman mutations, bestowing an assortment of superpowers in residents of Smallville, Kansas) and also a versatile substance in the development of radical new technology, specifically in the experiments carried out by LuthorCorp.