Simple stain

The simple stain is a cell staining technique used in microbiology to colorize cells of microbes.

Background
Cells are normally translucent or transparent, so without colorization of the cells with a staining method, it would be difficult to see the cells if viewed using a common light microscope.

Technique
In the simple stain technique or method, a small quantity of cells from a microbial culture or cell growth source is dispersed onto a single drop of water on a clean glass slide and allowed to air dry for 5-10 minutes or until all liquid has evaporated.

The slide is then briefly passed over a flame source (cell source facing upward)--this is called heat fixation, and helps the cells to better adhere to the glass. A dye (stain) solution such as crystal violet, safranin, or a similar dye is flooded onto the surface to cover the cells and allowed to bathe the cells for a minute or two before being rinsed or washed off. These dyes work well on bacteria because they have color-bearing ions (chromophores) that are positively charged (cationic). The slide is allowed to dry, and can then be viewed with a light or brightfield optical microscope so that the cells can be observed and studied.