The Notch pathway is essential for maintaining NPCs in the developing brain. Activation of the pathway is sufficient to maintain NPCs in a proliferating state, whereas loss-of-function mutations in the critical components of the pathway cause precocious neuronal differentiation and NPC depletion. Modulators of the Notch signal, e.g., the Numb protein are able to antagonize Notch effects, resulting in the halting of cell cycle and differentiation of NPCs. Conversely, the fibroblast growth factor pathway promotes Notch signaling to keep stem cells of the cerebral cortex in the proliferative state, amounting to a mechanism regulating cortical surface area growth and, potentially, gyrification. In this way, Notch signaling controls NPC self-renewal as well as cell fate specification.