Crystal violet is the stain used in Gram staining. When virions are coated with stain (positive staining), fine detail is obscured. This stain is commercially sold as a kit for staining gels. Tissue fixation is required for certain procedures such as antibody-linked immunofluorescence staining. Auramine-rhodamine staining and fluorescence microscopy are also used. AA can be identified by immunohistochemistry staining. They include microscopy, staining, and detection of antibodies. Thioflavins are dyes used for histology staining and biophysical studies of protein aggregation. It is, however, not ideal for immunohistochemistry staining. The dyes used in negative staining are acidic. Phosphomolybdic acid is used as a reagent for staining phenolics in thin layer chromatography. The cytoplasm is full of granules that assume a characteristic pink-orange color with eosin staining. The rash disappears after a few days with no staining or peeling of the skin. Obstacles include getting freeze artifacts on tissue that may interfere with proper mRNA staining. The use of the reagent results in blue staining.