Artificial life, or a-life, is an interdisciplinary science focused on artificial systems that mimic the properties of living systems. In the 1990s, new media artists began appropriating and adapting the techniques of a-life science to create a-life art; Mitchell Whitelaw's Metacreation is the first detailed critical account of this new field of creative practice. A-life art responds to the increasing technologization of living matter by creating works that seem to mutate, evolve, and respond with a life of their own. Pursuing a-life's promise of emergence, these artists produce not only artworks, but generative and creative processes: here creation becomes metacreation. Whitelaw presents a-life art practice through four of its characteristic techniques and tendencies. "Breeders" use artificial evolution to generate images and forms, in the process altering the artist's creative agency. "Cybernatures" form complex, interactive systems, drawing the audience into artificial ecosystems. Other artists work in "Hardware," adapting Rodney Brooks's "bottom-up" robotics to create embodied autonomous agencies. The "Abstract Machines" of a-life art de-emphasize the biological analogy, using techniques such as cellular automata to investigate pattern, form and morphogenesis. In the book's concluding chapters Whitelaw surveys the theoretical discourses around a-life art, before finally examining emergence, a concept central to a-life, and key, it is argued, to a-life art.