In the span of just three decades, scientific understanding of the formation of embryos has undergone a major revolution. The implications of these new research findings have an immediate bearing on human health and future therapies, yet most nonscientists remain quite unaware of the exciting news. In this engaging book, a distinguished geneticist offers a clear, jargon-free overview of the field of developmental biology. Benny Shilo transforms complicated scientific paradigms into understandable ideas, employing an array of photographic images to demonstrate analogies between the cells of an embryo and human society. Shilo's innovative approach highlights important concepts in a way that will be intuitive and resonant with readers' own experiences. The author explains what is now known about the mechanisms of embryonic development and the commanding role of genes. For each paradigm under discussion, he provides both a scientific image and a photograph he has taken in the human world. These pairs of images imply powerful metaphors, such as the similarities between communication among cells and among human beings, or between rules embedded in the genome and laws that govern human society. The book concludes with a glimpse of promising future possibilities, including the generation of tissues and organs for use as "spare parts."