Robert Brown was looking at a CELL NUCLEUS through a microscope.
Robert Brown (1773-1858) was a Scottish botanist. Studying the cells of plants, he called the ovals inside those cells the "nucleus" as he watched the interaction of pollen with the cell nucleus. The small, random oscillations of particles in the fluid of the cell are given the name "Brownian motion" based on the sort of fluctuating movement that Brown observed.
He was looking through a microscope at particles trapped in cavities inside pollen grains in water. The concept of Brownian motion is named after him. This is the random motion of particles suspended in a fluid, liquid or gas resulting from their collision with the fast-moving molecules. Here, the patterns of motion of the particles are typically alternations between random fluctuations in a particle's position inside a fluid sub-domain with a relocation to another sub-domain. Each relocation is followed by more fluctuations within the new closed volume.
