Physicists are able to cool some gases down to less than one-millionth of a degree above absolute zero by stopping their atoms with lasers and magnetic fields. These atoms then all achieve a collective quantum state, similar to a huge quantum wave, called the Bose-Einstein condensate. Condensates are very helpful quantum simulators: we use them to recreate more complex situations that we yet fail to fully understand in quantum mechanics, such as superconductors or other properties of a solid.