http://forum.wgbh.org/wgbh/forum.php?lecture_id=3170

In 1905, there were prominent scientists who did not believe in atoms. Einstein did. His April and May papers were motivated in part to support the concept of atoms. The April paper, Einstein's dissertation and one of his most cited papers, shows how the dimensions of a sugar molecule, suspended in water, can be determined. His method had many practical applications, hence the citations. In the May paper, a pollen particle took the place of a sugar molecule. For decades, the irregular, zig-zagging motion of pollen particles was a mystery. In a paper that is magic, Einstein showed how, with a simple ruler and a stopwatch, one could witness atoms at work and prove their existence.