Origins of the pituitary gland Placodes are specializations of the head ectoderm that are considered the source of many vertebrate novelties, including the nose, lens, ear, and hormone-producing portion of the pituitary. However, the presence of a pituitary-like structure in nonvertebrate chordates, derived instead from the endoderm, had suggested that the pituitary may predate placodes. Fabian et al. performed lineage tracing, time-lapse imaging, and single-cell messenger RNA sequencing to show that both endodermal and ectodermal cells can generate hormone-producing cells of the zebrafish pituitary. These experiments support that the vertebrate pituitary arises through interactions of an ancestral endodermal protopituitary with newly evolved placodal ectoderm. Science , this issue p. 463