Evolutionary Developmental Biology (Evo-Devo) deals with the relationships between the individual development and the phenotypic changes of the organism during evolution. Major morphological transitions in evolution are presently recognized to be accommodated by a few key developmental genetic changes (part of a "developmental reprogramming") and "case studies' in snakes, ducks, bats, dolphins, insects, and finches, providing examples of developmental bases of evolutionary change, are presented. On the other hand, the molecular changes occur in an otherwise conserved developmental genetics tool-kit (e.g., the Hox genes for anterior-posterior patterning, the network for eye formation) representing the "deep homology" underlying diversity of forms. Based on a relationship between embryo development and organism evolution, Evo-Devo represents a synthesis between Developmental and Evolutionary Biology.