The diversification of cortical interneuron subtypes begins during embryonic development as they become post-mitotic, continuing through to adulthood as they integrate into cortical circuits. Research from our lab and others demonstrates that their specific identities arise from the interplay between evolving intrinsic gene regulatory networks (GRNs) and non-autonomous cellular interactions. These interactions range from initial somal contacts as interneurons settle within the cortex to the later establishment of synaptic connectivity within functional ensembles. A fundamental principle of this maturation is that interneurons interact closely with the pyramidal neurons they eventually partner with. Consequently, the determination of interneuron identity and the wiring of cortical circuits are two profoundly interconnected processes