[
Nature,
1993]
Twenty years ago Sydney Brenner described an electrode-less plan for attacking the problems of neural development and physiology in the small nematode Caenorhabditis elegans. He proposed to set the groundwork by reconstructing the entire nervous system of the worm by serial section electron microscopy. Given the resulting wiring diagram, he thought it might be possible to make guesses as to how the nervous system worked. A second aspect of his plan was genetics: single-gene mutants exhibiting aberrant behaviour, such as uncoordinated movement, were to be analysed to address the question of how genes specify development and function of the nervous system. In two papers beginning on page 334 of this issue, McIntire et al. demonstrate that work on Brenner's plan, with a few tricks added over the years, is progressing very nicely.