Kryptonite is a fictional mineral from the Superman comic book series, known for its ability to weaken the superhero Superman. Originating from the destroyed planet Krypton, this green crystal emits radiation that is harmful to Kryptonians, causing them physical pain and reducing their powers. In the broader context of storytelling, "kryptonite" has come to symbolize any weakness or vulnerability that a person or character may have. It represents a critical flaw that can be exploited by adversaries, making it a common trope in various narratives beyond superhero genres.