Developmental processes are the series of biological changes associated with information transfer, growth, and differentiation during the life cycle of organisms. Information transfer is the transmission of DNA and other biological signals from parent cells to daughter cells. Growth is the increase in size due to cell expansion and cell division. Differentiation is the change of unspecialized cells in a simple body pattern to specialized cells in more complex body pattern. While nearly all organisms, even single-celled bacteria, undergo development of some sort; the developmental process of complex multicellular organisms is emphasized here. In these organisms, development begins with the manufacture of male and female sex cells. It proceeds through fertilization and formation of an embryo. Development continues following birth, hatching, or germination of the embryo and culminates in aging and death.

People have long been interested in the connection between the development of an organism...