Theodor Schwann was a pioneer of cell theory and the first scientists to articulate that cells--one type of which are now known as Schwann cells--comprise the nerve sheath.

Schwann was a shy child, preferring to absorb 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 eventually gave up theology to study medicine at the University of Bonn, where he enrolled in premedical studies and graduated in 1831.

While in Berlin, Germany, Schwann attended clinical demonstrations of Johannes Müller and began preparing a dissertation under Müller's guidance. Schwann's dissertation, De necessitate aeris atmosphærici ad evolutionem pulli in ovo incubato, involved a study of the breathing of the embryo in a hen's egg. After his graduation, Schwann immediately became Müller's assistant and devoted...