How do schools of fish swim in harmony? And how do the tiny cells in your brain give rise to the complex thoughts, memories, and consciousness that are you? Oddly enough, those questions have the same general answer: emergence, or the spontaneous creation of sophisticated behaviors and functions from large groups of simple elements. Like many animals, fish stick together in groups, but that's not just because they enjoy each other's company. It's a matter of survival. Schools of fish exhibit complex swarming behaviors that help them evade hungry predators, while a lone fish is quickly singled out as easy prey. So which brilliant fish leader is the one in charge? Actually, no one is, and everyone is. So what does that mean? While the school of fish is elegantly twisting turning, and dodging sharks in what looks like deliberate coordination, each individual fish is actually just following two basic rules that have nothing to do with the shark: one, stay close, but not too close to your neighbor, and two, keep swimming. As individuals, the fish are focused on the minutiae of these local interactions, but if enough fish join the group, something remarkable happens. The movement of individual fish is eclipsed by an entirely new entity: the school, which has its own unique set of behaviors. The school isn't controlled by any single fish. It simply emerges if you have enough fish following the right set of local rules. It's like an accident that happens over and over again, allowing fish all across the ocean to reliably avoid predation.