Esculin sesquihydrate is primarily used in laboratory settings as a fluorescent marker. It is often employed in histology and cytology to stain and visualize biological tissues under a microscope, particularly in studies involving blood vessels and lymphatic systems. The compound’s ability to fluoresce under ultraviolet light makes it valuable for tracking and identifying specific structures in cellular and tissue samples. Additionally, esculin sesquihydrate is utilized in microbiology as a component of selective media to differentiate certain bacterial species, such as Enterococcus, based on their ability to hydrolyze esculin in the presence of β-glucosidase. Its applications extend to pharmacological research, where it is studied for its potential antioxidant and anti-inflammatory properties.