From the early 1920s, Cartier worked closely with Jaeger LeCoultre to reinvent the lady's diamond dress watch, montre baguette. By creating the smallest movements possible and pushing the boundaries of watchmaking innovation, the smallest of these movements being the Calibre 101. Developed in 1929, it is the world's smallest mechanical movement. Composed of 74 parts and weighing barely 1 gram, this revolutionary movement was used for small, often highly jeweled lady's wristwatches.
Cf. J. Barracca, G. Negretti, F. Nencini, Le Temps de Cartier, Wrist International Srl, Milan, 1989, pp. 134-135