In an osmic acid stain, what color represents fats?

In an osmic acid stain, fats are represented by the color black. Osmic acid, also known as osmium tetroxide, is a lipid-specific stain that reacts with the double bonds in unsaturated fats, forming a black precipitate. This property is particularly useful in histopathology for visualizing fat deposits within tissue sections. The black color enables clear differentiation of lipid-rich areas from other cellular components, thereby enhancing the understanding of the tissue's overall morphology.

Other colors mentioned, such as red or blue, are typically associated with different histological stains that highlight proteins or nucleic acids rather than lipids. Therefore, recognizing that black is indicative of fat localization in tissues stained with osmic acid is essential for accurate interpretation in histopathology.