What technique involves freezing and fracturing specimens for examination under an electron microscope?

The technique that involves freezing and fracturing specimens for examination under an electron microscope is known as freeze etching. This method allows for the preservation of cellular structures in a way that maintains their natural state, which is crucial for high-resolution imaging. In freeze etching, specimens are rapidly frozen, and then subjected to a vacuum where a portion of the ice is sublimated away, revealing fine structural details of the specimen. This process creates a replica of the specimen’s surface and allows researchers to examine the internal structures with minimal distortion.

Cryo-sectioning, although it involves freezing, refers specifically to the process of cutting thin sections of frozen tissue for analysis, rather than fracturing the specimen. Embedding tissue involves using paraffin or resin to support the samples prior to sectioning, which does not align with the freezing and fracturing technique. Microtomy is the technique of cutting very thin sections of material but does not incorporate the freezing aspect integral to freeze etching. Thus, freeze etching is the most appropriate choice in this context.