The development and evolution of the human neocortex involve the expansion of the outer subventricular zone (OSVZ), a proliferative region outside the ventricular epithelium. This expansion increases neuron number and modifies the trajectory of migrating neurons, contributing to the larger and more folded structure of the human neocortex compared to other mammalian species. Recent studies have identified two main types of progenitor cells in the OSVZ: radial glia-like (oRG) cells and intermediate progenitor cells (IPs). oRG cells undergo multiple rounds of asymmetric division, generating IP cells, which then undergo symmetric divisions to produce neurons. The OSVZ's role in neocortical expansion is supported by genetic studies in ferrets, where similar features were observed. Molecular regulators, such as Notch signaling and β-catenin signaling, play crucial roles in maintaining the identity of oRG cells and promoting their proliferation. Understanding these mechanisms is essential for elucidating the evolutionary changes that led to the neocortical expansion in humans.The development and evolution of the human neocortex involve the expansion of the outer subventricular zone (OSVZ), a proliferative region outside the ventricular epithelium. This expansion increases neuron number and modifies the trajectory of migrating neurons, contributing to the larger and more folded structure of the human neocortex compared to other mammalian species. Recent studies have identified two main types of progenitor cells in the OSVZ: radial glia-like (oRG) cells and intermediate progenitor cells (IPs). oRG cells undergo multiple rounds of asymmetric division, generating IP cells, which then undergo symmetric divisions to produce neurons. The OSVZ's role in neocortical expansion is supported by genetic studies in ferrets, where similar features were observed. Molecular regulators, such as Notch signaling and β-catenin signaling, play crucial roles in maintaining the identity of oRG cells and promoting their proliferation. Understanding these mechanisms is essential for elucidating the evolutionary changes that led to the neocortical expansion in humans.