The development of photochemical theory through generations of scientists illustrates well the slow construction of science that Wald highlighted in his Nobel Lecture. In this view, each scientist contributes some part to the larger understanding of a phenomenon. Boll and Kühne knew in 1877 that rhodopsin was a photosensitive pigment in the retina with a reversible cycle of bleaching and regeneration. Following from these two, Hecht’s achievement was formalizing that cycle of bleaching and regeneration in photopigments almost 50 years after it had been first observed. And, after Hecht, George Wald, over the next 50 years, would fill in the mechanical and molecular details of that cycle.