Microscopy

A microscope is the indispensable tool of cell biology, because almost everything this chapter describes is far too small to see with the unaided eye. The name itself comes from the Greek mikros (small) and skopein (to see). Every optical microscope works by exploiting basic properties of light and glass lenses - reflection, magnification and numerical aperture - to bend and focus light in a way that makes a tiny object appear much larger and, ideally, sharper. Two quantities matter most when judging how useful a microscope actually is. Magnification is simply how much bigger the image looks compared to the object as seen by the naked eye; a high magnification with a blurry image, however, is not very useful. Resolution (or resolving power) is the more meaningful number - it is the ability of the lens system to show two very closely spaced points as genuinely separate, rather than blurring them into one smudge, and it depends on the wavelength of light used and the numerical aperture of the lens: the shorter the wavelength and the higher the numerical aperture, the finer the detail that can be resolved. The rest of this section works through five distinct kinds of microscope - bright field, dark field, phase contrast, and the two electron micr …