Calcofluor White staining is observed under which microscope?

• A. Light microscope
• B. Fluorescence microscope
• C. Electron microscope
• D. Phase-contrast microscope

Answer: (B)

Calcofluor White is a fluorescent stain that binds to fungal cell wall polysaccharides like chitin and cellulose. When excited by ultraviolet or blue light, it emits blue fluorescence, so you need a fluorescence microscope to visualize it. A standard light microscope won’t reveal the stain’s signal, and electron or phase-contrast microscopes do not detect this fluorescence. In short, the emission of light from the dye under specific excitation makes the fluorescence microscope the appropriate instrument.