The tourbillon was invented by Abraham-Louis Breguet and patented on 26th June 1801 as a way of cancelling out the variations in the going rate of a pocket watch in vertical positions, which were caused by the effects of gravity. It consists of a mobile carriage on which all the components of the regulating organ, including the escapement and the balance spring. The escape wheel pinion revolves around the fourth wheel, which is fixed. The carriage usually completes one rotation every 60 seconds and by turning cancels out the variation in rate in vertical positions. This complicated and delicate mechanism (Breguet only produced 35 in his lifetime) is one of the most ingenious in the world of watchmaking. A more simplified and more robust version is the carrousel, in which the rotating mechanism is governed by the third wheel rather than the fourth wheel. The tourbillon is available with lever and detent escapements.
Although the original tourbillon was designed to compensate for rate variations in vertical positions for a pocket watch (which, by definition spent the majority of its time in those vertical positions in one's pocket), tourbillons have been adapted for use in wristwatches to compensate for the effects of gravity in a multitude of different positions. A number of brands have even improved on the 200 year-old concept by creating gyrotourbillons that revolve around two or even three different axes at different speeds. Jaeger-LeCoultre, for example, has a strong record in the production of ever-faster gyrotourbillons.
Jaeger-LeCoultre Reverso Gyrotourbillon