The pituitary is an organ dual of origin. The anterior lobe (adenohypophysis) is epithelial in origin, whereas the posterior lobe (neurohypophysis) derives from the neural ectoderm. Precise spatial and temporal co-ordination of transcription factor expression in both structures is critical for pituitary formation and the differentiation of hormone-producing cells. Disruption of this regulation, for instance by mutation, can lead to numerous developmental disorders. We provide an overview of the molecular drivers of pituitary organogenesis and illustrate the anatomy and histology of the mature pituitary, comprising adenohypophysis (anterior lobe), neurohypophysis (posterior lobe), pars intermedia and infundibulum (pituitary stalk). For complete coverage of this and related areas of Endocrinology, please visit our free web –book, www.endotext.org.