Some types of matter aren’t so familiar in our daily experience—at low temperatures electrons can, metaphorically, feel the wind as another electron whizzes past, pulling them into a collective rhythm that allows them to flow without resistance in a superconductor. Some emergence shows organization in time rather than space, such as evolution: over many lifetimes, living things interact with their surroundings to produce the opposable thumb, the peacock’s tail. The individual cells of the human body renew themselves every few years, but the entity that is “you” never ceases to exist. Companies acting in their own self-interest interact with consumers to form an economy. In all these examples, out of the jumble of individual experience comes the coherent humming of collective behavior. Even conscious thought itself may be emergent: One neuron blindly fires chemical signals to its neighbors; but hundreds of neurons firing in chorus, their signals looping back upon themselves along grooves worn in the brain over time, create thought and memory.