The use of a fluorescence microscope to observe fungi makes it possible to highlight the fluorescence of the usual elements that can be found there, such as basidia, cystidia, asci, etc. These observations show the particular colors taken by these elements under the observation conditions and above all make it possible to locate them exactly on the preparation. It is an excitation of fluorescence by ultraviolet light, without adding fluorochrome: the collected light comes from the fluorescence emitted in return by the sample. This technique is also called autofluorescence or epifluorescence. This observation method could make it possible to better observe the activity of celles during division or their enzymatic and metabolic functions, which have been poorly observed in vivo until now, to explain these phenomena.