Used as a redox indicator in analytical chemistry, methylene blue indicator solution changes color in response to oxidation-reduction reactions. It is commonly employed in titrations involving reducing agents, where it shifts from colorless (reduced form) to blue (oxidized form), providing a clear visual endpoint. It is also used in biological staining to differentiate cells or tissues under the microscope and in microbiology to test the metabolic activity of microorganisms. In environmental applications, it helps assess the oxygen demand in water samples. Additionally, it serves in educational labs to demonstrate redox processes and electron transfer reactions.