The sinoatrial node is still setting the pace 100 years after its discovery.

See related article, pages 1605–1614 The mammalian sinoatrial node, the pacemaker of the heart, was discovered 100 years ago in the countryside of Kent (UK) in “a cosy, squat, red-roofed farm-house, embowered in creepers, separated from the road by a richly stocked garden” with “a horse going round and round winding up a huge bucket from a very deep well” and a “farmyard, filled with healthy farmyard manure”.1 Arthur Keith (later Sir Arthur) had converted the drawing room into a laboratory and recruited the assistance of Martin Flack, the son of the local butcher and grocer and a young medical student at the time.1 One evening when Keith and his wife, Celia, returned from a bicycle ride, Flack showed him a “wonderful structure” he had discovered in the heart of a mole (perhaps caught on the farm?)—so was discovered the sinoatrial node. Keith and Flack published the discovery of the sinoatrial node in 1907 in the Journal of Anatomy and Physiology .2 Curiously, only a few years later, Keith was to become embroiled in one of the biggest scientific scandals of all time, ‘Piltdown man’, a fraudulent ‘missing link’. Now 100 years after the discovery of the sinoatrial node, we are still making new discoveries about the workings of the sinoatrial node as shown by the paper from Ju and Allen and colleagues in this issue of Circulation Research —the sinoatrial node is still setting the pace!3 In the 1970s and 1980s a flurry of voltage clamp studies, first on multicellular preparations of sinoatrial node tissue and then on isolated sinoatrial node cells, appeared to establish the mechanism of pacemaking in the sinoatrial node.4 At this time, pacemaking was primarily thought to be result of the decay of delayed rectifier K+ current (K …