Development refers to the processes by which genes give rise to phenotypes.
Evolution, thus, depends on the relationship between genes and phenotypes, that is, on development. The organization of the genotype-phenotype map determines the ability of a system to evolve, since it determines how phenotypes vary with genotypes. A further twist arises when the genotype-phenotype map itself evolves. The importance of evo-devo has been recognized already at the end of the 19th century, but the questions were too far ahead of the experimental techniques of the time. Current renewed and vigorous interest in evo-devo is driven by the spectacular progress in experimentally probing the molecular mechanisms of the cell and their genetic underpinnings.