Used primarily in histology for staining cell nuclei in tissue sections. It provides a strong blue-black to black coloration of chromatin, making nuclear details highly visible under the microscope. Commonly applied in routine tissue examination and in specialized staining protocols such as the Verhoeff–Van Gieson stain for elastic fibers. Its durability and contrast make it ideal for long-term tissue preservation and diagnostic pathology. Often used in combination with counterstains to differentiate tissue structures clearly.