The hypothalamus is involved during the coordination of neuroendocrine functions in vertebrates and their evolutionary origin can be described using integrated transcriptome or connectome brain maps of swimming tadpoles of Ciona intestinalis, also known as sea vase. These organisms serve as an approximation of their ancestral protovertebrate. The map included several cell types relative to different regions of the vertebrate hypothalamus, including the mammillary nucleus, arcuate nucleus and magnocellular neurons. These observations highlighted how the hypothalamus predates the evolution of the vertebrate brain. The neural crest and cranial placodes are key innovations that contributed to the evolution of the vertebrate head. However, less is known about the evolutionary origin of the crown and summit of the vertebrate brain. In a new study now on Science Advances, Laurence A. Lemaire and a research team in molecular biology and integrative genomics at the Princeton University, New Jersey, U.S., used an extensive single-cell transcriptome fate map of the Ciona tadpole to characterize the neural cell types comprising its brain also known as the sensory vehicle.