Used in histology to detect polysaccharides and mucins in tissue sections. PAS stains glycogen, glycoproteins, and proteoglycans magenta, making it useful for identifying basement membranes, glycogen deposits, and fungal organisms. Alcian blue highlights acidic mucopolysaccharides and mucins in shades of blue, helping differentiate mucin types in epithelial tissues. Together, PAS and Alcian blue allow simultaneous visualization of neutral and acidic carbohydrates, commonly applied in gastrointestinal, pulmonary, and connective tissue studies to assess pathological changes like metaplasia or tumor mucin production.