One of the greatest physicists of the 20th century was John Wheeler. Wheeler was thinking about this quantum “weirdness,” about how these quanta sometimes behave as particles and sometimes as waves.
When he began to devise experiments that attempted to catch these quanta acting like waves when we expect particle-like behavior and vice versa.
Perhaps the most illustrative of these experiments is shown passing a photon through a beam splitter and into an interferometer, one with two possible configurations, “open” and “closed.”