The use of fluorescent stains to visually investigate eukaryotic and/or prokaryotic cells is increasing quickly and manuscripts within all areas of research publish results using fluorescent staining techniques. However, in contrast to literature on traditional histological staining techniques, the literature on fluorescent stains and staining techniques does not offer as good an illustration of cellular morphology. The aim of this guideline is to illustrate different fluorescent stains and staining techniques for imaging immune cells, in particular the polymorphonuclear leukocytes (PMNs), in combination with infecting bacteria as seen in chronic bacterial infections. Thereby providing the first guideline for the morphology and identification of fluorescently stained PMNs, bacteria and biofilm.