Background: SABC (StreptAvidin-Biotin Complex) is specially designed for displaying the distribution of antigens in tissues and cells in immunochemistry and other immunodetection analyses. This kit has high sensitivity because each complex it generates has a large number of FITC and streptavidin molecules. Compared to the traditional immunodetection using free FITC dyes, the SABC-FITC system greatly enhances the sensitivity and suppresses the background. FITC is at 490~495nm, emission at 520~530