We will concentrate mostly on ideas that led to wave-particle duality. Early experiments found that matter and light each seemed to have wave and particle properties: a contradiction. Here you will see how our greatest physicists struggled over those ideas. Many physicists will admit that this wave-particle problem has not been resolved to this day. The double-slit test is a popular way to express the wave-particle problem, but a far better test is the beam-split coincidence test. The history of that test will be shown, starting from the thought experiment of Einstein in his definition of the photon, leading to modern actualizations. This critical history includes objections and alternatives that were rejected. From the original offprints, you can judge the assumptions that IMHO led us astray. After you see my other writings and videos of experiments and theory, you might understand how these historical components lead to the resolution of wave-particle duality.