[ep103]

My high school science teacher told us that he was given the prize for the photoelectric effect because that was a well understood mechanism by the time of the awarding. It was generally understood that relativity was going to be a bigger deal (concept wise), but since it was still so hotly debated / not yet thoroughly accepted, the commission wanted to ensure that he was given a prize before death (the award is not given post-humorously for some reason) and given for something that wouldn't be later rejected.

[Retric]

"In 1905 Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets. This discovery led to the quantum revolution."

So, he basically described photons as a particle for the first time. That's also ridiculously huge. http://en.wikipedia.org/wiki/Photoelectric_effect Considering they had been generally thought of as a wave before that. (http://en.wikipedia.org/wiki/Maxwell%27s_equations) Setting the stage for a lot of wave / particle duality aka QM theory.

[Someone]

You are forgetting Sir Isaac :-)

I don't think he used the word photon, but he did describe light as particles, and had (flawed, but that is science) arguments for that (http://www.studyphysics.ca/newnotes/20/unit04_light/chp1719_...)