Sections intended for electron microscopy are typically cut to approximately which thickness?

• A. 90 micrometers
• B. 90 nanometers
• C. 9 nanometers
• D. 9 micrometers

Answer: (B)

Sections for electron microscopy must be ultrathin so electrons can pass through the sample without being scattered too much. In transmission electron microscopy (TEM), the beam needs to transmit the specimen, so the typical thickness is in the tens of nanometers range. About 90 nanometers fits this common ultrathin target, providing enough structural detail while still allowing electrons to transmit effectively.

Thicker sizes like micrometers would block or heavily scatter the beam, degrading image quality, while extremely thin coatings of a few nanometers are technically challenging to produce routinely and don’t align with standard practice for preparing biological or material sections. Therefore, around 90 nanometers is the standard approximate thickness for sections intended for electron microscopy.