During the course of the present proposal we first addressed the time-dependent recruitment of GABAergic neurons into early patterns of cortical correlated activity during development in vivo, to clarify whether there is a specific interneuron subtype that function as leaders (driver hub cells) in the initiation of correlated neuronal activities and their different implications concerning network synchronization. To this aim we used a multidisciplinary approach that combined: two-photon calcium imaging of cells activity in awake animals, genetically modified mice to target interneurons according to their spatial or temporal origin, electrophysiological recordings to stimulate or record interneurons, and several neuroanatomical techniques to characterize interneurons subpopulations. Our results point out that already at early stages of development cortical interneurons form functional and spatial assemblies that shape developmental activity (Figure 1). In the following step we addressed whether spatial embryonic origin of interneurons shape their impact on network dynamics. We report that neocortical driver hub cells (synchronization masters) arise from a particular embryonic region, the Medial Ganglionic Eminence (MGE). Such cells display unique properties that make them key regulatory masters coordinating correlated activity in the maturing neocortex. In summary, work performed under the current proposal adds to our understanding regarding maturation of cortical circuits by linking interneurons development and circuit physiology and supposes a step forward towards the understanding of pathophysiology of neurological disorders. Results from the present proposal have been disseminated among the scientific community in several workshops and international conferences.