Reproduction in mammals is dependent on specific hypothalamic neurons secreting gonadotropin-releasing hormone (GnRH). During embryonic development, GnRH neurons originate in the nose and migrate to the brain. Here, they release GnRH into the pituitary portal blood circulation for delivery to the pituitary, thus inducing the secretion of fertility-related hormones. Although this system is well studied in mice and other mammals, very little is known about human GnRH neuron development. Here (p. 3969), Paolo Giacobini and colleagues undertake a detailed analysis of the GnRH system in first-trimester human embryos by tracking the origin, migration pattern, final destination and number of GnRH neurons. By applying 3D imaging of solvent-cleared organs (3DISCO) technology to human foetuses for the first time, the authors gain unprecedented insights into the development of the GnRH system, including identifying unexpected migratory routes and brain locations of GnRH neurons. Intriguingly, the authors find a greater number of GnRH neurons than previously thought and reveal that only approximately 20% of these cells colonise the hypothalamus by the end of the first trimester, with the rest being quite widely distributed. While the long-term fate and function of these extra-hypothalamic GnRH neurons remains unclear, their presence raises the possibility of non-fertility-related roles for the GnRH system.