The mammalian neocortex shows six-layered cytoarchitecture and contains more than 20 billions of neurons (excitatory neurons; 80%, inhibitory interneurons; 20%). Excitatory neurons are further categorized into diverse subtypes laid out in a layer specific manner, which differ in their morphologies, projection patterns, and electrophysiological properties. For example, callosal projection neurons extend their axons contralaterally to make inter-hemispheric connections while corticospinal motor neurons extend long-range projections to the spinal cord. Interestingly, during the embryonic brain development, all of these neuronal subtypes are generated by sequential divisions of a single class of neural progenitor. This fact raises one important question; what is the mechanism that determines the neuronal fate? In other words, how do daughter neurons differentiate into distinct subtypes after born from the same mother? In this class, I would like to discuss how neuroscientists have unraveled this mystery, by reading one paper that identified a key regulator gene, Fezl (also known as Fezf2, ZNF312), expression of which is necessary and sufficient to convert immature neurons to one specific subtype, corticospinal motor neurons.