Used primarily in histology and cytology for staining cellular structures, this solution imparts a pink to red color to cytoplasmic components and extracellular materials like collagen. It serves as a counterstain in H&E (hematoxylin and eosin) staining, one of the most common techniques in tissue examination under the microscope. The contrast between the blue nuclei (from hematoxylin) and the pink cytoplasm (from eosin) allows pathologists to identify tissue abnormalities, including tumors and inflammatory conditions. Its water-soluble nature makes it suitable for use in protocols where alcohol-based solutions are not preferred, and it is compatible with aqueous mounting media. Also used in blood smear analysis and microbiology for differentiating cell types and detecting morphological changes.