What is the technique shown in the image?

• A. Oil Red O
• B. Sudan I
• C. Prussian blue
• D. Alcian blue

Answer: (A)

This image demonstrates a lipid-staining technique. Oil Red O is a fat-soluble dye used to visualize neutral lipids—triglycerides and cholesterol esters—in tissue. It stains these lipid droplets bright red, which stands out clearly against a counterstain like hematoxylin. This staining works best on fresh or frozen tissue because routine paraffin processing dissolves lipids, making frozen sections the appropriate preparation for viewing fat. The other stains shown target different substances: Prussian blue highlights iron, Alcian blue stains acidic mucopolysaccharides, and Sudan dyes are also used for lipids but Oil Red O in frozen sections is the classic, widely used method for demonstrating neutral lipids.