It was during the Renaissance that images and pictures were first used by anatomists, microscopists, and astronomers as scientific tools. In that era, scientific images served as a kind of inventory of the known world. In the 19th century, the popularization of scientific ideas gave science a new vigor. Photographic images gave science a new reality, explaining and legitimizing scientific concepts--movement, for example--to a fascinated public. In our days, the scientific image is often a construction--helping us to represent objects and ideas that, like fractals or black holes, cannot be defined through actual observation. Monique Sicard is Projects Director at CNRS Images Média.