Which instrument is used to prepare ultra-thin sections for electron microscopy?

• A. Rotary microtome
• B. Ultramicrotome
• C. Cryostat
• D. Vibratome

Answer: (B)

Ultra-thin sections are required for transmission electron microscopy because electrons must pass through the specimen with minimal scattering. The instrument designed for this level of thinning is the ultramicrotome. It cuts resin-embedded samples with a diamond knife to produce ultrathin ribbons on the order of tens of nanometers, which are then placed on EM grids for staining and imaging. The other instruments serve different purposes: a rotary microtome makes thicker sections for light microscopy, a cryostat produces frozen sections for rapid diagnosis, and a vibratome cuts thicker, often unfixed or live-tissue sections. So the ultramicrotome is the tool used to prepare ultra-thin sections suitable for electron microscopy.