OverviewEnterprises in Photonics and Quantum Technology increasingly rely on use of photons. Definitions, and views, of photons have undergone a remarkable change during the last century, continuing today with advances in nanotechnology and lasers. Our Changing Views of Photons: A Tutorial Memoir describes the changing views of the physics community toward photons, and how photons are viewed today in several contexts. The first portion of the book, a memoir with few equations, presents a story of the changing view of physicists toward radiation and its photons, written for those with interest but possibly without technical background. A second portion, of tutorial appendices, explains, from an elementary start, the background of quantum theory and radiation needed for those whose profession involves photonics and who want an explanation of the theory that contemporary physics requires for that subject.