The diverse size and shape of sessile marine organisms such as the seaweeds shown here are strongly influenced by their environment as well as their genome. The Algorithmic Beauty of Seaweeds, Sponges, and Corals, edited by Jaap A. Kaandorp and Janet E. Kübler (Springer, $49.95, £35), describes how simulation models can throw light on the growth and structure of these organisms, with particular emphasis on seaweeds, sponges and corals.