The patterns on the shells of tropical sea snails are not only compellingly beautiful but also tell a tale of biological development. The decorative patterns are records of their own genesis, which follows laws like those of dune formation or the spread of a flu epidemic. Hans Meinhardt has analyzed the dynamical processes that form these patterns and retraced them faithfully in computer simulations. His book is exciting not only for the astonishing scientific knowledge it reveals but also for its fascinating pictures. An accompanying CD-ROM with the corresponding algorithms offers wide scope to those who wish to try their hand at simulating and varying the patterns.