Understanding normal development is fundamental to appreciating postnatal morphology, physiology and, in some instances, pathophysiology. Developmental biology tends to interrogate models in nonprimate species, for instance the mouse, where genetic manipulation gives privileged insight into the function of particular genes. Some human developmental processes, as occur in the adrenal gland, are not faithfully reproduced in these rodent models, yet have an impact on the pathophysiology and treatment of endocrine disorders, such as congenital adrenal hyperplasia. In this setting, in vitro research of normal human development complements clinical investigation of patients born with congenital disorders.