Discovery of Colloids.

While employed in a glassworks (1897) Zsigmondy directed his attention to colloidal gold present in ruby glass, and he discovered a water suspension of gold. He theorised that much could be learned about the colloidal state of matter from studying the manner in which the particles scatter light. To facilitate such study, he and Heinrich Siedentopf developed the ultramicroscope (1903), and Zsigmondy used it to investigate various aspects of colloids, including Brownian motion. His work proved particularly helpful in biochemistry and bacteriology.