The main purpose of staining a specimen on a microscope slide is so that it can be better viewed. The stain usually colors one part of the specimen, but not another part. By creating that color contrast it becomes easier to view parts of the subject. Sometimes a certain part of a specimen cannot be seen, even with a microscope, so it has to be stained a certain color so that it can be viewed and studied. Most stains may be used on non-living specimens, though only some stains will work on living specimens.
Common Stain Purposes
Stains are often used in the medical field to view how infected samples react to treatment. Since it may be difficult to follow the reactions, a dye is often used to make the process more clear. Alternatively, stains may be used on dead cells for education purposes. Different stains may be used to highlight parts of a cell so that students can see them in color. Whatever the purpose of staining a slide is, however, the reason for the staining always boils down to making it easier for the viewer to observe the specimen in some fashion.
There are quite a number of steps involved in properly staining a specimen that will be viewed through a microscope. The first step is permeabilization, which is when the sample is treated with a surfactant. This chemical breaks down cell walls and allows in larger molecules of dye. The next step is fixation, where a chemical fixative is added which will create chemical bonds between proteins and enhance their rigidity. The samples must then be mounted on a microscope slide, though the samples may be grown directly on the slide. The last step is applying an appropriate stain which will color cells, tissues, components, or processes (in living cells).