Brownian motion
While Jan Ingenhousz described the strange motion of coal dust particles on the top of alcohol in 1785, the discovery of this is often given to the botanist Robert Brown in 1827. Brown was studying pollen grains of the plant Clarkia pulchella suspended in water under a microscope when he observed minute particles, ejected by the pollen grains, executing a jittery motion. By repeating the experiment with particles of inorganic matter he was able to rule out that the motion was life-related, although its origin was not known yet.