Since its early days, photography has been both, tool for and subject of scientific research. Developments in photochemistry, camera construction and lenses made photography an extremely successful mass medium. At the same time, photography served scientific research as a key medium for observation, documentation, education and communication. ETHBibliothek, the main library at the Swiss Federal Institute of Technology Zurichs (ETH Zurich), is holding in its Image Archive vast collections of photographs. Among them is the complete, and so far only little examined, collection of ETH Zurichs own Photographic Institute throughout its existence as an independent service and research unit between 1886 and 1979. The new, third volume in the series Pictorial Worlds. Photographs from the Image Archive, ETH-Bibliothek documents both main aspects of scientific photography: servicing research in many disciplines and being subject of basic research itself. A rich selection of images is presented, ranging from astronomical and micro photography to laboratory situations and carefully illuminated experimental installations. The introductory essay investigates the interplay between photography and the world of science and tells the story and changing role over the decades of ETH Zurichs Photographic Institute. The book received an award from the Stiftung Buchkunst in the 2013 competition Most Beautiful Books from Germany.