 The study shows that using intersectional genetics with the gene ID2, researchers can access and experimentally study a fourth group of cortical GA biagic interneurons, INS, that includes neuroglyiform cells, NGFCs. These NGFCs express high levels of neuropeptide Y, NPY, have a late-spiking firing pattern, extensive local connectivity and are distinguished by their activity during NREM sleep. The study also highlights the diversity and properties of non-NGFC ID2 INS that correspond to a diverse group of INS that strongly expresses the neuropeptide CCK. This article was authored by Robert McHald, Shlomo Dellel, Manuel Valero, and others.