Used as a vital stain in histology to visualize cell structures under the microscope, particularly in H&E (hematoxylin and eosin) staining. It colors cytoplasm and extracellular matrix pink or red, helping distinguish them from nuclei, which are stained by hematoxylin. Commonly used in pathology for tissue diagnosis and cancer detection. Also applied in microbiology to stain blood smears and in some immunological techniques. Its alcoholic formulation improves tissue penetration and is preferred in certain fixation protocols. Additionally, used in some dermatological tests and educational labs for demonstration of cellular morphology.