Microorganisms in their natural state, are colorless, and nearly invisible to the naked eye, even under a light microscope. To make them visible, the cell structures have to be contrasted from their environment by applying chromogenic dye or stains, and the technique is called staining.
Staining helps to differentiate various morphological types (by shape, size, arrangement, etc.), determine the staining characteristic of the organism, and demonstrate the purity of the culture. Staining also gives a presumptive idea for direct diagnosis of infections and aids in the study of various internal and external structures of microorganisms such as cytoplasmic membrane, nucleus, flagella, capsule, endospores, etc.
