We have continued our study to identify the molecular mechanisms that regulate cortical neuron fate specification. We have discovered/confirmed that (1) Early cortical progenitors are multipotent, and they give rise to different types of cortical project neurons and glia based on birthdates. There is no evidence of intrinsically lineage-restricted early neural stem cells; (2) expression of Fezf2, a major cell fate determining gene for cortical neurons, is regulated by multiple enhancers and promoters. These enhancers and promotor region have distinct and sometimes overlapping activity; (3) transcription factor Nfib is essential for the differentiation of neural stem cells and required for the cortical neurons to extend corticofugal axons; and (4) splicing factor Tra2b is essential for the survival and differentiation of cortical neural progenitor cells. These results provide novel insights into the development of cortical neurons.