The mechanisms underlying the temporal specification of neural stem cells (NSCs), a process by which a single progenitor can generate different types of neurons and glia in an invariant order, are still poorly understood in mammals. However, in the past decade, work on Drosophila NSCs, called neuroblasts, has identified a series of sequentially expressed transcription factors that lies at the heart of this phenomenon. Here, I highlight some key findings that illuminate the role of these transcription factors during development and the regulatory principles allowing them not only to promote neuronal diversity but also to control the final number of neurons in the different regions of the nervous system. Ultimately, and given recent evidences of evolutionary conservation, cracking the temporal specification code of Drosophila neuroblasts may provide new perspectives for the safe manipulation of human NSCs and their therapeutic use.