Pierre Rossier was a pioneering Swiss photographer whose albumen photographs, which include stereographs and cartes-de-visite, comprise portraits, cityscapes and landscapes. He was commissioned by the London firm of Negretti and Zambra to travel to Asia and document the progress of the Anglo-French troops in the Second Opium War and, although he failed to join that military expedition, he remained in Asia for several years, producing the first commercial photographs of China, the Philippines, Japan and Siam (now Thailand). He was the first professional photographer in Japan, where he trained Ueno Hikoma, Maeda Genzō, Horie Kuwajirō, as well as lesser known members of the first generation of Japanese photographers. One of his works became the earliest known hand-coloured Japanese photograph. In Siam, Rossier took ethnographic portraits for French zoologist Marie Firmin Bocourt, who was on a scientific expedition. In Switzerland he established photographic studios in Fribourg and Einsiedeln, and he also produced images elsewhere in the country. Rossier is an important figure in the early history of photography not only because of his own images, but also because of the critical impact of his teaching in the early days of Japanese photography.