A magnetic lens consists of electromagnets and is utilized in electron microscopes, such as the transmission electron microscope (TEM), to focus the electron beam onto the specimen. This magnetic mechanism replaces the traditional glass lenses used to focus light in optical microscopes.

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The transmission electron microscope (TEM) is a type of electron microscope that functions analogously to a brightfield microscope. It utilizes an electron gun to release an electron beam that is directed from above the specimen and focused using a magnetic lens. The electrons pass through the specimen and are then projected onto a detector to capture the image. TEM is particularly useful for observing small, thin specimens, such as tissue sections and subcellular structures.

Transmission Electron Microscope (TEM)

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Magnetic Lens

For a transmission electron microscope (TEM) to function properly, the specimen and the electron beam must be placed in a vacuum. Additionally, the specimen must be fully dehydrated and cut extremely thin, typically between $${}20-100$$ nm thick, to allow the electrons to successfully pass through it.

TEM Specimen Requirements

In transmission electron microscopy (TEM), contrast is artificially enhanced by staining specimens with electron-dense materials containing heavy metal atoms, such as uranyl acetate or osmium tetroxide, rather than colored dyes. Prior to this staining process, the extremely thin sample sections are typically secured to fine copper wire or carbon-fiber grids to support them during observation.

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