How are the many distinct cell types that characterize a mature nervous system genetically specified? For a terminally differentiating neuron this question boils down to a gene regulatory question: how is the expression of the distinct batteries of genes that define the terminal, functional properties of a distinct neuron type induced and maintained? Using genetic loss-of-function approaches in the nematode C.elegans, my laboratory has begun to uncover what appear to be simple, phylogenetically conserved principles underlying the generation of diverse neuronal identities.