Sample Preparation Into Ultra-thin Sections. Contents Introduction Tissue selection Fixation Glutaraldehyde Osmium tetroxide OsO4 Potassium permanganate - KMnO 4 Acroline Embedding Dehydration Resin infiltration Polymerization Ultramicrotomy Trimming the capsule Making glass knives Thin sectioning Staining sections Miscellaneous procedures Thick sections - light microscopy Whole mounts on coated grids Arts and Formulae Photography Developing film Developing prints

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Introduction. The Electron Microscope was developed from the coalescence of several scattered ideas and hypotheses. The electron itself was discovered at about 1897 and was shown to have wave properties in 1924. Much of the early work with electrons centered on how to generate electrons and how to deflect or aim them. Various "lens" were contrived and by 1931, two German scientists were demonstrating the "first" EM which was largely a modified oscillograph. No specimens could be viewed but it was predicted that an electron microscope would have much better resolution than the light microscope. By the late 1930's and early 1940, commercial EMs were available with moderate resolution. These were used mainly to study electron optics and to make improvements. Procedures for specimen preparation came much later. For the biologist, the EM is one of the most powerful tools available for cell and tissue studies. It should be realized that electron microscopy is not a science on its own, but merely a technique or tool. A thorough understanding of the EM and of cells and their ultrastructures are an asset to understanding most other areas of biology. There are now many types of electron microscopes, but the two most common types are the transmission electron microscope (TEM or just EM) and the scanning electron microscope (SEM). Simply put, the SEM scans the surface of coated specimens with an electron beam and by detecting electrons scattered (reflected) by the object, forms an image on a TV like monitor. This image is usually aesthetically pleasing and has a resolution of 50 µ and up. The TEM transmits a beam of electrons through a specimen and forms an image based on the removal of electrons from the beam by the specimen (basically a high resolution shadow). Resolution can attain