The patterns on the shells of tropical sea snails are not only beautiful but tell the tale of biological development. The decorative patterns are records of their own genesis, which follow their own laws. Hans Meinhardt has analyzed the dynamical process that form these patterns and retraced them faithfully in computer simulations. His book reveals scientific knowledge and fascinating pictures. An accompanying diskette with the corresponding algorithms offers wide scope to those who wish to try their hand at simulating or varying the patterns.