Brownian motion as noted by Robert Brown (1773- 1858), the Scottish botanist who discovered the phenomenon. The plot shows the positions of three microscopic pollen grains, suspended in water, as observed at 30 second intervals. The grains are seen to be in ceaseless random motion. Observing this erratic movement of pollen, Brown discovered Brownian Motion in 1827. Fifty years later it was realised that the pollen was being buffeted by the random movements of water molecules in the fluid. This effect gave the first direct demonstration of the existence of molecules.