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Stains or dyes are used in biological and medical disciplines to highlight cell structures and organelles, cells, or tissues for viewing, usually with an instrument such as a microscope. In vivo staining is the process of dyeing living tissues—in vivo means "in life" (compare with in vitro staining). By causing certain cells or structures to take on contrasting color(s), their form (morphology) or position within a cell or tissue can be readily seen and studied. The usual purpose is to reveal cytological details that might otherwise not be apparent; however, staining can also reveal where certain chemicals or specific chemical reactions are taking place within cells or tissues.
More often, these stains are called vital stains. They are introduced to the organism while the cells are still living. However, these stains are eventually toxic to the organism, some more so than others. To achieve desired effects, the stains are used in very dilute solutions ranging from 1:5,000 to 1:500,000 (Howey, 2000). Note that many of these stains are also used as in vitro stains.
Basic biological vital stains Different stains react or concentrate in different parts of a cell or tissue, and these properties are used to advantage to reveal specific parts or areas.
Crystal violet Crystal Violet
Iodine Iodine is used in chemistry as an indicator for starch. When starch is mixed with iodine in solution, an intensely dark blue color develops, representing a starch/iodine complex. Starch is a substance common to most plant cells and so a weak iodine solution will stain starch present in the cells. Iodine is one component in the staining technique known as Gram staining, used in microbiology.
Lugol's solution or Lugol's iodine (IKI) is a brown solution that turns black in the presence of starches and can be used as a cell stain, making the cell nuclei more visible.
Methylene blue Methylene blue is used to stain animal cells, such as human cheek cells, to make their nuclei more observable. It is less toxic than iodine, for example.
Nile blue
Rhodamine Rhodamine
Others Bismarck Brown
Malachite Green
Carmine Alum
Eosin Yellowish
Methyl Green
Neutral Red
Hematoxylin
Safranin
See also
External links Vital Staining for Protozoa and Related Temporary Mounting Techniques (http://www.microscopy-uk.org.uk/mag/artfeb00/rhvital.html) ~ Howey, 2000 | 
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