A pioneer of avant-garde photography and a former student of the German chemist August Wilhelm Hofmann, Alfred Stieglitz is a prime example of how artists related to, and challenged, the status of photographic representations at the turn of the 20th century. In this paper I examine Stieglitz’s contribution to modernist photography and avant-garde art in light of his early engagement with experimental science, and claim that his scientific training shaped his experimental aesthetics. I argue that the conceptual development of his works was strongly informed by an approach to visual representations as experimental practices, which ultimately fed into his own definition of “experimental aesthetics”. I conclude with some remarks on how Stieglitz’s photography challenged concepts such as scientific observation and scientific objectivity, and suggest possible ways in which the history of photography may offer a productive ground to reconcile historical and philosophical accounts of representative practices across art and science.