Abstract
Colloidal gold probes have revolutionized electron immunocytochemistry and are now used extensively for microbiological studies. The gold probes can be applied in one of several methods to gain valuable information from the sample. The pre‐embedding technique, the post‐embedding technique, the immunonegative stain technique, the immunoreplica technique and the immunofreeze‐fracture technique, are each described and their applications in microbiology, for diagnosis, for the detection of the site of antigen synthesis in host cells, for vaccine production and for genetic engineering are reported.