The cellular properties of neural progenitor cells have been best characterized in the telencephalon, the most complex region of the vertebrate brain. In recent years, several transcription factors, including Mash1, Ngn1/2, Pax6 and Emx1/2, and signaling molecules, such as Notch and bone morphogenetic proteins, have emerged as important players in key areas of telencephalic development. These include the specification of positional identity, the proliferation of neural stem cells and their commitment to a neuronal or glial fate, and the differentiation of layer-specific neuronal phenotypes in the cerebral cortex.