Lugol’s solution, named after French physician J. G. A. Lugol, is widely used in various applications. It is most commonly known as an antiseptic, disinfectant and starch indicator. Lugol’s solution affects the carbohydrate molecules in the following way: iodine binds to complex carbohydrates (starch in plant organisms, glycogen in animals), staining them in the process. Lugol’s solution is an aqueous solution of iodine and potassium iodide. It is used in parasitology for staining parasites in stool samples, in zoology for staining protozoic organisms in order to enhance the contrast of internal structures (nuclei and glycogen vacuoles) and for preserving the protozoa, and in microbiological testing Lugol’s solution is one of the components of Gram staining.