The cerebral cortex contains two main neuronal cell populations: the excitatory pyramidal neurons and the inhibitory interneurons, which constitute 20-30% of all cortical neurons. Cortical interneurons are characterized by a remarkable morphological, molecular and functional diversity. A swathe of research activity over the last 20 years has sought to determine how cortical interneurons acquire their mature cellular and functional features, and has identified a number of transcription factors that function at different stages of interneuron development. Here, we review all current knowledge concerning the multiple functions of the "master regulator" - LIM-Homeodomain transcription factor Lhx6 - a gene expressed in the medial ganglionic eminence of the basal telencephalon that controls the development of somatostatin and parvalbumin expressing interneurons.