ABSTRACT
The development of histological techniques for the past five centuries was propelled by the invention of the microscope and the improvement of its magnification and resolution. The greatest improvement of methods, allowing observation of plant and animal tissues, dates from the 18th and 19th centuries; whereas in the 20th century mainly the development of electron microscopical and other methods such as fluorescence and freezing techniques, as well as histochemistry and immunohistochemistry proceeded.
Independent of the microscope type used for the observation each sample requires specific histoprocessing techniques including fixation (chemical or physical), dehydration (e.g. in series of alcohols), embedding (e.g. in paraffin wax or plastic media) and staining (e.g. hematoxylin and eosin, trichrome methods, toluidine, and methylene blue etc.).
High resolution and magnification achieved in transmission electron microscopy requires specific methods of fixation (e.g. double fixation with glutaraldehyde and osmium tetroxide), infiltration and embedding in polymerizing plastics like epoxy or acrylic resins, cutting for ultrathin sections with diamond knifes and contrasting with uranyl acetate and lead citrate, whereas samples for scanning electron microscopy require drying after dehydration and vacuum sputtering with carbon or gold before observation.
