The brain's ability to fulfil highly sophisticated tasks requires a profuse number of different neuron types that display an exquisite degree of specialisation. In my lab we study how the terminal identity of each neuron type is established during development and maintained throughout the life of the animal. We also are interested in understanding the molecular mechanisms that drive the emergence of new neuronal types, novel functions and innovative behaviours in evolution. In our studies we take advantage of the small genome size of Caenorhabditis species, their amenability to genetic manipulations and the invariable cellular lineage, that consistently generates 302 neurons classified into 118 neuron types, to gain insights into these processes at the single-cell level and across species.