For staining myelin, sections should be cut at what thickness?

• A. 10-15 nm
• B. 1-2 μm
• C. 5-10 μm
• D. 50-100 μm

Answer: (A)

Section thickness determines whether the staining and the microscope will work well. For staining myelin with routine light microscopy, you want sections in the micrometer range so the stain can penetrate evenly and light can pass through easily. A typical thickness is about 5–10 micrometers. If sections are too thick, staining may be uneven and image clarity suffers due to light scattering. If they’re too thin, there may not be enough tissue mass to generate good contrast.

The nanometer-scale option is relevant to electron microscopy, where ultrathin sections are used to let electrons transmit and reveal ultrastructure, but that’s a different modality with different preparation and staining requirements. So for standard light-m microscopy staining of myelin, around 5–10 micrometers is the appropriate thickness.