What happens when a gas is cooled to absolute zero? A new door to the quantum world opens up because all the atoms start "marching in lockstep", forming one giant matter wave  the Bose-Einstein condensate. This was predicted by Einstein in 1925, but only realized in 1995 in laboratories at JILA in Boulder and at MIT. Since then, many properties of this mysterious form of matter have been revealed, including matter wave amplification and quantized vortices. Bose condensates have been used to realize a basic atom laser, an intense source of coherent matter waves.