The development of microscopy and cell-staining techniques made possible impressive advances in our understanding of microorganisms. That fact should hardly be surprising. The microscope allows one to see structures too small to be visible with the naked eye; individual cells, for example. But those small structures are usually colorless and transparent, making it difficult to distinguish specific features contained within them. Thus, it became important to find ways of bringing out these features so that they could be studied in more detail. The father of microscopy, Antoni van Leeuwenhoek, found that dyeing muscle fibers with saffron allowed him to see the detailed structure of the fibers more easily.

From van Leeuwenhoek's time to the mid-nineteenth century, scientists searched for natural products to use in dyeing cells. They were only moderately successful until the discovery of the first synthetic dye by William Perkin in 1856. Then the new...