The study of light has been an important part of science from its beginning. The ancient Greeks and, prior to the Middle Ages, Islamic scholars provided important insights. With the coming of the Scientific Revolution in the 16th and 17th centuries, optics, in the shape of telescopes and microscopes, provided the means to study the universe from the very distant to the very small. Newton introduced a scientific study also of the nature of light itself. Today, optics remains a key element of modern science, not only as an enabling technology, but in quantum optics, as a means of testing our fundamental understanding of quantum theory and the nature of reality itself.