Eosin B is primarily used as a biological stain in histology and cytology for visualizing cellular structures under a microscope. It is often employed in combination with other dyes, such as hematoxylin, to provide contrast in tissue samples, highlighting cytoplasm, collagen, and muscle fibers. In microbiology, it aids in distinguishing different types of cells and tissues. Additionally, Eosin B finds application in the textile industry as a dye for fabrics and in the manufacturing of inks and pigments. Its ability to bind to proteins and other cellular components makes it a valuable tool in both scientific research and industrial processes.