Counterstaining involves the use of two or more stains in succession, each of which colours different cell or tissue constituents. Temporary staining is used for immediate microscopical observation of material, but the colour soon fades and the tissue is subsequently damaged. Permanent staining does not distort the cells and is used for tissue that is to be preserved for a considerable period of time.
Electron stains, used in the preparation of material for electron microscopy, are described as electron-dense as they interfere with the transmission of electrons. Examples are lead citrate, phosphotungstic acid (PTA), and uranyl acetate (UA).
"staining." A Dictionary of Biology. . Encyclopedia.com. (April 20, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/staining
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