Theodor Schwann was a German physiologist widely credited for establishing the cell as the fundamental unit of animal structure, helping in the development of cell theory in the process. His other accomplishments included coining the term metabolism, discovering the digestive enzyme pepsin, founding modern histology, classifying yeast as an organic substance and determining that embryonic cells form the basis of all adult animal tissues. He lived to be 72 years old, from 1810 to 1882.
Schwann's 1839 signature work, "Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants," extended German botanist Matthias Jacob's assertion that cells made up all plant life to animals as well. Schwann concluded that yeast spore formation was indicative of life processes, becoming one of the first to contribute to germ theory of alcoholic fermentation. He also discovered striated muscle in the upper esophagus and the myelin sheath covering peripheral axons, ultimately classified as Schwann cells. He founded the basic principles of embryology by observing that the egg is one cell eventually capable of becoming a multicellular organism.
Schwann was born to a goldsmith in Neuss, Germany. He enjoyed working with his hands from a young age. Schwann studied medicine at the universities of Bonn, Wurzberg and Berlin. Schwann graduated in 1834 and took a job in a Berlin anatomy museum before being appointed as a professor of anatomy at the University of Leuven, Belgium in 1838. He moved to the University of Liege in 1882, where he taught both anatomy and physiology.
Later in life, Schwann developed a keen interest in theology. He continued to work with cells until his death in 1882.