Upon his return to France in 1890, Calmette met Louis Pasteur (1822–1895) and Emile Roux (1853–1933), who was his professor in a course on bacteriology. He became an associate and was charged by Pasteur to found and direct a branch of the Pasteur Institute at Saigon (French Indochina), in 1891. There, he dedicated himself to the nascent field of toxicology, which had important connections to immunology, and he studied snake and bee venom, plant poisons and curare. He also organized the production of vaccines against smallpox and rabies and carried out research on cholera, and the fermentation of opium and rice.