In 1930, Frits Zernike developed a way of making the invisible visible: he had perfected a method for the examination of living, unstained cells. The human eye and brain are good at distinguishing the amount of light (contrast) or its wavelength (colour), but are unable to distinguish differences in phase (there is no common name for it). Zernike had invented a technique that would make the invisible phase difference of a living cell a visible difference in light and shade. He took his invention, which he called phase contrast, to the greatest microscope manufacturer, Carl Zeiss, in 1932. Zeiss told him to get lost.

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