Zernike, Frits, 1888–1966, Dutch physicist, Ph.D. Univ. of Amsterdam, 1915. He was on the faculty at the Univ. of Groningen from 1915 until his retirement in 1958. Zernike received the 1953 Nobel Prize in Physics for demonstrating the phase-contrast method and inventing the phase-contrast microscope. The new technology offered improvements over the conventional optical microscope by transforming effects due to changes in the optical path, which the eye cannot detect, into changes in light intensity, which the eye can detect. The phase-contrast microscope allowed scientists to study the internal structure of living cells by eliminating the need to stain and thereby kill the cells.