<P> Phase - contrast microscopy is an optical microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image . Phase shifts themselves are invisible, but become visible when shown as brightness variations . </P> <P> When light waves travel through a medium other than vacuum, interaction with the medium causes the wave amplitude and phase to change in a manner dependent on properties of the medium . Changes in amplitude (brightness) arise from the scattering and absorption of light, which is often wavelength - dependent and may give rise to colors . Photographic equipment and the human eye are only sensitive to amplitude variations . Without special arrangements, phase changes are therefore invisible . Yet, phase changes often carry important information . </P> <P> Phase - contrast microscopy is particularly important in biology . It reveals many cellular structures that are not visible with a simpler bright - field microscope, as exemplified in the figure . These structures were made visible to earlier microscopists by staining, but this required additional preparation and killed the cells . The phase - contrast microscope made it possible for biologists to study living cells and how they proliferate through cell division . After its invention in the early 1930s, phase - contrast microscopy proved to be such an advancement in microscopy that its inventor Frits Zernike was awarded the Nobel Prize in Physics in 1953 . </P> <P> The basic principle to making phase changes visible in phase - contrast microscopy is to separate the illuminating (background) light from the specimen - scattered light (which makes up the foreground details) and to manipulate these differently . </P>

Where would phase contrast microscopy improve image quality