What paraffin section thickness is used for the Osmium Tetroxide fat staining protocol?

• A. 2 micrometers
• B. 4-5 micrometers
• C. 6-8 micrometers
• D. 10-12 micrometers

Answer: (A)

Thickness of paraffin sections governs how well osmium tetroxide can diffuse and bind lipids. For osmium tetroxide fat staining, you want very thin sections so the fixative penetrates quickly and stains lipids evenly, producing clear, dark labeling of fat with minimal diffusion artifacts. About 2 micrometers is ideal because it allows complete osmication without the diffusion limitations that thicker sections would impose.

If sections were thicker, such as 4-5 micrometers or more, OsO4 penetration becomes slower and uneven staining can occur, leading to patchy or weak fat visualization. The thicker the section, the greater the chance of incomplete osmication and inconsistent results, which is why thinner sections are preferred for this protocol.