Reductionism—breaking things into their component parts to study how they work—is an effective tool in physics. But many real-world challenges resist this approach. All too often, large scale behavior emerges in ways that are difficult to predict from the behavior of individual components. When the computational requirements are too massive or the theories that govern the component parts are inadequate, many complex systems have yielded to the physics of emergence, which seeks organizing principles at the system level. Find out how many different phenomena—superconductors, hydrodynamics, and even the formation of structure in the universe—are all fruitful areas where the physics of emergence is leading to new understanding.