In the second half of nineteenth century, scientists proved that specific bacterial organisms caused specific diseases, and the field of microbiology was on its way to becoming a distinct science. The microscope was also further developed during that time, and scientists were concerned with identifying and classifying bacteria. Most bacteria are difficult to see with a compound microscope, but can be seen when there is obvious contrast between the bacteria cells and their surrounding medium. Various dyes are used to stain cells so that they are more easily seen. As early as the late eighteenth century, scientists had developed some basic methods of staining cells to aid in their study and used natural substances such as saffron which stained some parts of a cell. The discovery of synthetic dyes in the mid-1800s enabled scientists to utilize more colors to stain cells.

In 1884, the Danish physician...