Theodor Schwann was born in Neuss, Germany, in 1810. He was a shy child, preferring to lose himself in his studies, his family, and religion rather than deal with the outside world. He left his hometown to attend the Jesuit College in Cologne, Germany, in 1826. Schwann gave up theology to study medicine at the University of Bonn, where he enrolled in premedical studies and graduated in 1831.

While in Berlin, he attended the clinical demonstrations of Johannes Müller and began preparing a dissertation under Müller's guidance. After his graduation, Schwann immediately became Müller's assistant and devoted all his time to research. Around 1834, Schwann became interested in digestive processes. Within two years, he had isolated a chemical (called pepsin) from the stomach lining that he thought was responsible for the digestion of protein. This was the first time an enzyme had ever been isolated from...