Zernike, Frits (1888-1966) was a Dutch physicist who made important discoveries in optics, the branch of physics concerned with light and vision. He was awarded the Nobel Prize in physics in 1953 for developing the phase-contrast microscope, which later proved useful for cancer research.

Zernike was born July 16, 1888, in Amsterdam, the Netherlands, to Carl Frederick August Zernike and Antje (Dieperink) Zernike. At 19, Zernike won a gold medal for an essay on probabilities from the University of Groningen. He studied physics at the University of Amsterdam, receiving a Ph.D. degree in 1915. In 1920, he became a professor at the University of Groningen, where he stayed until retirement in 1958.

In the 1930's, Zernike invented the phase-contrast microscope, though its importance was not recognized until the 1940's. This microscope changes the phase relationship between the light waves passing through the specimen and those not passing through it. This action makes some parts of the specimen appear brighter and other parts darker than normal. Parts of a transparent object that vary in thickness or have certain other optical properties can be made visible in this way.

This instrument makes it possible to study colorless, transparent objects, such as living tissues, that would be invisible under an ordinary microscope unless they were stained. Scientists can now study microscopic organisms without first killing them, which often occurred in the staining process.

Zernike died on March 10, 1966, at Naarden, the Netherlands.