From tower clocks to wristwatches, the history of clock- and watch-making over the past four centuries chronicles the ever-increasing miniaturisation of mechanisms. Up until now, the power needed to drive a wristwatch mechanism has been a limiting factor in terms of design and innovation. Greubel Forsey’s fundamental work on Mechanical Nano, based on the mastery of energy and available space, is once again confirmed and now applied in a watch mechanism.