Holography is a much broader field than most people have perceived. Recording and displaying truly three-dimensional images are only small parts of it. Holographic optical elements (HOE) can perform the functions of mirrors, lenses, gratings, or combinations of them, and they are used in myriad technical devices. Holographic interferometry measures microscopic displacements on the surface of an object and small changes in index of refraction of transparent objects like plasma and heat waves. Future photonic devices such as electro-optical chips will undoubtedly incorporate micro-lasers and HOEs for optical computations, free-space interconnects, and massive analog and digital memory systems.