Practice question

Transmission electron microscopy achieves nanometer resolution but demands electrons to traverse specimen, requiring extreme thinness and contrast enhancement. Biological tissues are first fixed, dehydrated and embedded in resin, then cut into 60-90 nanometer ultrathin sections with diamond knife. Sections are mounted on grids and stained with heavy metals like osmium tetroxide, uranyl acetate and lead citrate that scatter electrons, delineating membranes, ribosomes and chromatin. Unlike light methods that handle whole mounts or living cells, this invasive preparation sacrifices viability but reveals mitochondrial cristae, nuclear pores and virus particles with exquisite ultrastructural detail.