A micro-rotor is a compact winding rotor embedded within an automatic movement rather than mounted on top, allowing for thinner watch cases.
A micro-rotor is a miniaturized automatic winding weight integrated within the movement's plane rather than mounted on top. Made from dense metals (gold, platinum) to maximize efficiency despite reduced size, it allows significantly thinner automatic watch cases while maintaining self-winding capability.
Micro-rotors enable ultra-thin elegant designs and showcase movement finishing through exhibition casebacks. However, they're less efficient at winding than full-sized rotors, may require more wrist movement, and are significantly more expensive to manufacture. It's a design choice prioritizing aesthetics over winding efficiency.
Piaget pioneered micro-rotors in the 1960s and remains a leader. Other notable examples include Bulgari Octo Finissimo, Chopard L.U.C., Jaeger-LeCoultre Master Ultra Thin, and various high-end independent watchmakers. These movements are exclusive to luxury segments due to manufacturing complexity.