Understanding how genetic variation acts through development to produce morphological variation is a central challenge in developmental biology. The relationship between genotype and phenotype is both complicated and simplified by development. Canalization, or the suppression of the phenotypic effects of genetic variants and gene interactions greatly complicate the genetics of complex traits, confounding prediction of variation. On the other hand, integration, or the tendency for development to produce correlated variation, simplifies genotype-phenotype maps. This is because integration reflects the convergence of multiple genetic influences on processes that produce coordinated variation among morphological traits. This talk reports results from our work on the developmental-genetic basis for variation in craniofacial form.