Methylene blue is used as a dye in different staining procedures viz. Wright's stain and Jenner's stain. It also serves as an indicator and medicine. Further, it is used to examine RNA and DNA under the microscope or in a gel. It is widely used as a redox indicator in analytical chemistry. It acts as a photosensitizer utilized to generate singlet oxygen in order to make organic peroxides by a Diels-Alder reaction. It is also used in the sulfide analysis. It plays an important role in aquaculture to treat fungal infections. Methylene blue is used as a dye in different staining procedures viz. Wright's stain and Jenner's stain. It also serves as an indicator and medicine. Further, it is used to examine RNA and DNA under the microscope or in a gel. It is widely used as a redox indicator in analytical chemistry. It acts as a photosensitizer utilized to generate singlet oxygen in order to make organic peroxides by a Diels-Alder reaction. It is also used in the sulfide analysis. It plays an important role in aquaculture to treat fungal infections.