Swiss botanist and pioneer of submicroscopic morphology, who helped to initiate the study later known as molecular biology.

Frey-Wyssling was educated at the Swiss Federal Institute of Technology Zürich (ETH Zürich), the University of Jena, and the Sorbonne. From 1928 to 1932 he was a plant physiologist at Medan, Sumatra. He became a lecturer at ETH Zürich (1932), served as a professor in the department of botany and plant physiology (1938–70), and was also rector of the institution (1957–61).

In 1938 Frey-Wyssling began his studies in submicroscopic morphology, using polarizing microscopy and other optical techniques to obtain indirect evidence concerning submicroscopic structures. He held that the studies of histologists (those who deal with tissue-level structures discernible through the microscope) and of physiological chemists, who study submicroscopic structures, would eventually be unified on the level of macromolecular chemistry. This subject, later known as molecular biology, became a practical reality with the application of the electron microscope (1940) and with techniques, such as ultracentrifugation, that allowed the separation of cellular components for direct physiological and biochemical analysis. Frey-Wyssling found that the basic concepts he had evolved from his indirect methods were corroborated by the direct imaging of submicroscopic structures with the electron microscope. He wrote several books based on his submicroscopic studies.