The challenge of fusion energy is often equated to capturing—and holding—lightning in a bottle. The analogy is apt. Lightning and a fusion energy plasma have a lot in common. Similarities include very high temperatures, massive electric charges, and extremely complex fluid dynamics. Researchers at the DIII-D National Fusion Facility found another characteristic shared between the two types of plasmas: an odd electromagnetic wave known as a whistler. If their theories are correct, the whistler discovery could help better understand runaway electrons in tokamaks. It could even help control these destructive particles.