This book is the first comprehensive attempt to consider the development of organisms as a multi-level feedback-linked self-organizing process. Accordingly, the data related to morphogenetic cell activities and to the development of entire organisms are reconsidered and reformulated in terms of theories of symmetry and self-organization, which is described in non-specialist terms. An important role for biomechanical feedback is emphasized. Two opposing approaches to development are outlined, a 'genocentric' one and a 'morphocentric' one, and the possibility of their combination is discussed. Unlike other books recently published in biotheoretical and biomathematical fields, this book is centered around developmental problems. This title is intended for students and researchers in biology, biomechanics and mathematical modelling.