Embryogenesis is the biological process of fundamental importance for the growth of life. This book is a collection of views on contemporary trends in modern biology, emphasizing on gametogenesis, fertilization, early and/or delayed embryogenesis in animals, plants and other small organisms. Written by international experts, this book provides an introduction as well as in-depth review on classical as well as contemporary problems that pose a challenge in understanding how living organisms - take birth, grow, and reproduce at levels varying from molecular and cellular levels to individual level. Important topics covered are human embryogenesis, hox genes-master regulators of the animal bodyplan, plant somatic embryogenesis, genomic integrity of mouse embryonic stem cells, etc.