The exact origin of GABAergic (γ-aminobutyric-acid-releasing) interneurons, which are responsible for control the firing of the principal human cortical neurons, has remained unclear. In rodents all interneurons originate from a subcortical area known as the ganglionic eminence. But in 6 June Nature, Kresimir Letinic and colleagues from Yale University School of Medicine, show that in humans most of the GABAergic interneurons arise locally, from the cortical ventricular zone/subventricular zone (Nature 2002, 417:645-649).