ABSTRACT
Staining methods in current use have survived repeated methodological discontinuities. By the late 19th century stains using dyestuffs and silver salts were widely used. The purpose of biological staining is to generate information, most often to address the following questions. To provide answers a staining method must be sufficiently sensitive to detect the biological target. This often depends upon the amount of material present, and on the precise mode of action of the stain. The sizes of dye ions can control staining patterns, and the sizes of labeled antibody molecules critically influence sensitivity in the immunostaining of resin sections. Specimen geometry influences the staining process at a variety of scales. After block staining only superficial elements of the specimen are strongly stained. Specimen preparation also affects section geometry, and hence stains penetration. Surface topography of cryosections is usually more uneven than paraffin sections, which are themselves rougher than resin sections.
