It is not often that a computer screen saver can be used to solve problems in science, but this is the case with the technique described in this paper - Cellular Automata. The Cellular Automaton (CA) is widely known as the basis of the “Game of Life”, used as a screen saver on many computers. However, this technique from the field of Artificial Intelligence is much more than just entertainment. CAs have evolved from being a pencil-and-paper exercise into a valuable simulation tool. This paper, the third in a series on the way in which Artificial Intelligence (AI) may be used in science, outlines how CAs work and how they may be used to simulate and help us understand such processes as the growth of bacteria or the development of snowflakes.