In 1838, Schwann became professor at the University of Louvain, Belgium, and of Liège ten years later. He studies sugar and starch fermentation as biological processes, properties and activation of muscles, and nerve cells. The latter led him to the discovery of the so-called Schwann cells. He also coined the term metabolism for the chemical processes in a biological organism. Schwann also basically founded embryology, studying the development of a single egg cell into a complete organism. Also, he cofounded modern cell theory with Matthias Jakob Schleiden.