∞ generated and posted on 2016.01.14 ∞
Attachment of material to a microscope slide in such a manner that it is less likely to wash away in the course of staining and washing.
Typically fixing is accomplished using heat. Note though that as is also true with regard to cell numbers found in smears (not too many nor too few), ones goal in terms of heating is not too much nor too little. There also exist alternatives to heating as means of adhering cells, such as mixing with a sticky substance such as serum along with subsequent drying.