Methylene Blue trihydrate is widely used in medical settings as a diagnostic tool and treatment. It is employed as a dye in various staining procedures, particularly in microscopy, to enhance the visibility of cellular structures. In clinical practice, it is used to treat methemoglobinemia, a condition where blood cannot effectively carry oxygen, by converting methemoglobin back to hemoglobin. Additionally, it serves as an antidote for cyanide poisoning by forming a non-toxic complex with cyanide ions. In surgical procedures, it is utilized to identify sentinel lymph nodes in cancer surgeries, aiding in tumor localization. Beyond medicine, it is applied in aquaculture to treat fungal and parasitic infections in fish, ensuring healthier aquatic environments. Its versatility makes it a valuable compound in both healthcare and environmental management.