Final answer:
Transmission electron microscopy (TEM) offers high-resolution visualization of specimens as small as 0.1 nm, demanding very thin sample sections prepared through dehydration, embedding, and staining with electron-dense substances for contrast.
Step-by-step explanation:
Transmission Electron Microscopy
Transmission electron microscopy (TEM) is a technique that uses electrons to visualize specimens at magnifications and resolutions not achievable by optical microscopes. In a TEM, electrons emitted from a hot filament, also known as the cathode, are accelerated and pass through a specimen that must be ultrathin and examined in a vacuum. The transmitted electrons are then focused onto a detector, typically a fluorescent screen, photographic plate, or a CCD camera, and the image is transferred to a computer for viewing.
The resolution of TEM is one of its most significant features, as it can resolve details as small as 0.1 nm (10-10 m), which allows for magnifications of up to 100 million times the original object size. This high resolution has enabled scientists to observe individual atoms and detailed cell nuclear structures.
Sample preparation for TEM involves creating very thin sections of the specimen because electrons cannot pass through thick materials. Biological specimens, in particular, require careful processing involving dehydration and embedding in plastic resin. Sections are cut using an ultramicrotome and then stained with heavy metal containing substances that are electron-dense, such as uranyl acetate or osmium tetroxide, to increase contrast in the resulting image.