What is Histology?
[[File:Microscope with stained slide.jpg|thumb|220px|A stained histologic specimen, sandwiched between a glass [[microscope slide]] and [[cover slip|coverslip]], mounted on the stage of a light microscope.]] [[File:Emphysema H and E.jpg|right|220px|thumb|Microscopic view of a histologic specimen of human [[lung]] tissue stained with [[haematoxylin]] and [[eosin]].]] [[File:Masson's Trichrome Stain (Rat Airway Section).jpg|thumb|right|220px|'''Masson's trichrome''' stain of rat airway. [[Connective tissue]] is stained blue, [[Cell nucleus|nuclei]] are stained dark red/purple, and [[cytoplasm]] is stained red/pink.]] [[File:PurkinjeCell.jpg|right|220px|thumb|Drawing of [[Purkinje cell]]s (A) and granule cells (B) from pigeon cerebellum by Santiago Ramón y Cajal, 1899. Instituto Santiago Ramón y Cajal, Madrid, Spain]] [[File:HSP IF IgA.jpg|thumb|200px|right|Microphotograph of a '''histological section''' of human skin prepared for '''direct immunofluorescence''' using an anti-IgA [[antibody]]. IgA deposits are in the walls of small superficial capillaries (yellow arrows). The pale wavy green area on top is the [[epidermis]], the bottom fibrous area is the [[dermis]].]] '''Histology''' is the study of the microscopic [[anatomy]] of [[cells]] and [[tissue (biology)|tissues]] of [[plant]]s and [[animal]]s, particularly the tissues. It is a part of [[cytology]], and an essential tool of [[biology]] and [[medicine]]. Histology is usually done by looking at cells and tissues under a [[light microscope]] or [[electron microscope]]. The tissue has to be specially prepared beforehand. == The process == The stages below are only described in outline. Laboratories which do histology work from schedules which are much more detailed. === Fixing === Chemical fixatives are used to preserve tissue from [[decay]]. This preserves the structure of the cell and of sub-cellular components such as [[cell organelles]] (e.g., nucleus, [[endoplasmic reticulum]], [[mitochondria]]). The most common fixative for light microscopy is [[form