Histological stains were scare prior to the year 1850, yet there are several publications of very detailed observations of unstained tissues. Van Leewenhoek is credited with using the first histological stain; where he showed contrasting muscle fibers with the use of saffron in 1714-1719.

Necessity to stain tissue to view under the microscope:

Unstained tissue-nearly transparent
Stains are used to differentiate, highlight or selectively color desired tissue elements
Tissue elements react in certain predictable ways to chemicals and dyes-histochemical reactions
Histochemical reactions are exploited to indicate the presence of a selected tissue component