In 2000, with the completion of the human genome project, nine related channels were found to comprise the complete voltage-gated sodium gene family and they were renamed NaV1.1–NaV1.9. This millennial event reflected the extraordinary impact of molecular genetics on our understanding of electrical signalling in the nervous system. In this review, studies of animal electricity from the time of Galvani to the present day are described. The seminal experiments and models of Hodgkin and Huxley coupled with the discovery of the structure of DNA, the genetic code and the application of molecular genetics have resulted in an appreciation of the extraordinary diversity of sodium channels and their surprisingly broad repertoire of functions. In the present era, unsuspected roles for sodium channels in a huge range of pathologies have become apparent.