Basketball is an intricate, high-speed game filled with split-second, spontaneous decisions. But that spontaneity is possible only when everyone first engages in hours of highly repetitive and structured practice--perfecting their shooting, dribbling, and passing and running plays over and over again--and agrees to play a carefully defined role on the court. This is the critical lesson of improve, too, and it is also a key to understanding a puzzle of Millennium Challenge: spontaneity isn't random.