In 1903, the Parisian Edmond Jaeger (1858-1922) challenged the Swiss perceptions by inventing and manufacturing ultra-thin calibres. Jacques-David LeCoultre (1875-1948), grandson of the Manufacture’s founder, threw himself into the task with zeal. The collaboration led to a friendship between the two men and gave birth to some true marvels in watchmaking, culminating in the birth of the Jaeger-LeCoultre brand in 1937.