Zernike’s phase-contrast microscope

When Frits Zernike showed his newest invention to a German manufacturer of microscopes, they reacted with scepticism: ‘If this had any practical value, we would have invented it ourselves a long time ago.’

They couldn’t have been more wrong. Zernike’s phase-contrast microscope was a breakthrough in medical research. There was good reason that he was awarded the Nobel Prize for it in 1953. The medal is also on display.

The device made studying living cells possible for the first time. Until that time, cells could only be viewed under a microscope by adding colour, which killed them.

Zernike solved the problem by using the difference in phase that is created when light shines through a transparent object. It slows down a tiny bit compared to the surrounding light. Zernike enhanced the difference, thereby increasing the contrast. This way, it suddenly became possible to view a living cell without using colour.

Zernike developed his device all by himself. He liked to work at night, tinkering with his own contraptions and prototypes. More than once he combed his colleagues’ drawers and cabinets looking for parts. Supposedly, this is the reason he was not allowed his own key to the laboratory and why he would sometimes sneak in via the roof of the bicycle shed.