Immunocytochemistry and in situ hybridization are widely used biomedical sciences. They are essential in medical diagnosis and in cell biology research. Affinity labeling is the central goal of the experimental strategy involving a series of techniques in a logical order; from the effects of specimen fixation, through specimen preparation to expose the antigen, to optimizing immunolabeling, to assessing the result and finally to safety considerations. Numerous examples of these techniques in biomedical sciences are included, as well as experimental assays and practical tips. This survey of methods will serve as an invaluable reference source in any laboratory setting (academic, industrial or clinical) involved in research in almost every branch of biology or medicine, as well as in pharmaceutical, biotechnological and clinical applications.