It occurs to me that as audacious as Einstein's relativity and photoelectric effect papers were 100 years ago, taken together they're even more so. The relativity paper is fundamentally grounded in the electromagnetic wave theory of light, yet at the same time he had decided that this theory of light was inadequate. How could he have known that once all the details of his particle theory of light were ironed out, that the speed of photons would have to be the same in all frames? But he did. What a guy!