René Sim Lacaze trained at Atelier Mentel in Paris, which had close ties to Cartier, Boucheron and Janesich. In 1923 he began work at Van Cleef & Arpels, where he excelled in design drawing. By 1926, he became head of artistic and creative design. In 1941 he switched to Mauboussin while simultaneously running his own studio. He also designed pieces for Cartier, Sterlé and Harry Winston. Now regarded as one of the most important jewelry designers of the 20th century, he contributed iconic designs to several of the leading jewelry houses.