Malachite Green 5%, aqueous is a staining solution used in biological and microbiological research. The solution consists of 5% malachite green (CI No. 42000), a triphenylmethane dye dissolved in water.

Malachite green is widely used as a staining agent in microbiology for the study of bacteria and fungi. It binds to cell structures such as cell walls and cell membranes, and thus can help researchers better identify the morphology and structure of microorganisms. In addition, malachite green can be used in histology to stain specific tissues and structures, such as spores and endospores.

The 5% aqueous solution of malachite green provides effective and differential staining of microorganisms and tissues.