The ability to immunologically link microscopic tags to specific proteins has produced major advances in all forms of microscopy. Initially researchers needed to make and label their own antibodies. This required a good working knowledge of immunology. Today labeled anitbodies are readily available from a variety of vendors. Although this has greatly facilitated the expansion of immunolabeling techniques, it has also led to their use by researchers with little or no background in immunology. While this is not a problem for simple, straightforward situations, the quality of data produced in more specialized experiments can suffer.