Evolutionary computing, inspired by the biological world, is one of the emergent technologies of our time. Being essentially a software activity, it has been successfully applied, e.g. for optimization and machine learning in various areas. The tremendous increase in computational power and, more recently, the appearance of a new generation of programmable logic devices allow for a new approach to designing computing machines inspired by biological models: it is now possible to make the hardware itself evolve.This book is based on a workshop on evolvable hardware, held in Lausanne, Switzerland, in October 1995. It reports the state of the art of research in this field and presents two introductory chapters, written with the novice reader in mind.