This book is an introduction to cellular automata for students or scientists of any discipline wishing to simulate real or imagined systems with spatial extent. The concept of cellular automata is described in simple terms and the design decisions for using CA in simulation are discussed in detail. Hard- and software for cellular automata are presented with many examples are given, including reaction-diffusion systems, lattice gas models for fluid flow, traffic simulation, and others. Each chapter concludes with some exercise problems.