Of the great mysteries that face modern biologists, one of the most intriguing concerns the development of the microscopic embryo into exceedingly complex plants and animals--into roses and cacti, elephants and blue whales, apes and human beings. How does one cell give rise to so many millions of cells? How do they divide so as to form hearts, brains, eyes, and ears? Where in this pin-head-sized object is all this information encoded? Now, in The...