Which complication has been extensively researched and invented by the Greubel Forsey brand?

The tourbillon complication is recognized as a significant innovation in the world of high-end watchmaking, particularly associated with the Greubel Forsey brand. This complication was originally invented by Abraham-Louis Breguet in the late 18th century to counteract the effects of gravity on a watch's accuracy by mounting the escapement and balance wheel in a rotating cage. Greubel Forsey has made considerable contributions to this concept by enhancing its functionality and aesthetic, creating several complex iterations of the tourbillon that improve its precision and visual appeal.

The brand is known for its commitment to pushing the boundaries of traditional watchmaking, and the tourbillon designs they have developed reflect both technical mastery and innovative spirit, often featuring multiple tourbillons or unique configurations. This focus on the tourbillon demonstrates Greubel Forsey's dedication to horological excellence and their status as leaders in the field of luxury timepieces.