Arti?cial life is an interdisciplinary ?eld of science, hosting experts from c- puter science, biology, physics, chemistry, and mathematics, as well as phi- sophers and artists. It focuses on studying the phenomena of life on all levels of complexity and organization — molecular, cellular, organismic, and p- ulation. These studies not only employ conventional computers (using both software and hardware), but also take place in wetware, using techniques of biochemical laboratory. Arti?cial life research is not limited to life forms - isting on the Earth. It rather attempts to study the general principles of life which are common to all instances of life, both already recognized and yet unknown. This book is dedicated to the software medium, the most popular and widely employed in the arti?cial life research. The software medium o?ers almost unlimited abilities for experiments, which are cheap, easily arranged, and modi?ed. Additionally, such experiments canbe repeated under the same conditions, and large amounts of data (unavailable in biological studies) can be collectedfor analysis.To beginexperimentation,a modelof lifeis required. Such models are built in software for all organizational levels of life. Most of the models described in this book are very general and therefore allow for a wide range of experiments.