For the technique shown, at what section thickness should be cut?

• A. 10-15 nm
• B. 0.5-1 μm
• C. 1-2 mm
• D. 50-100 μm

Answer: (A)

For transmission electron microscopy, sections must be ultrathin so electrons can pass through the specimen and form a clear image. The interaction of electrons with matter is strong, so the slice has to be extremely thin—on the order of tens of nanometers. A thickness of 10–15 nanometers fits this requirement, providing enough transmission and high resolution for detailed cellular structure. The other thicknesses are too thick for electrons to traverse effectively; micrometer- or millimeter-scale sections are used for light microscopy or gross tissue examination, not for TEM. This is why the ultrathin nanometer range is the correct choice.