In a STED fluorescence light microscope pulses of excitation light (3) are applied to a sample, which excite fluorescent entities contained in the sample for fluorescence, and which are focused on at least one focal area. Further, de-excitation light (12) is applied to the sample, which de-excites the excited fluorescent entities and which comprises an intensity zero point in the at least one focal area, as a continuous wave. Fluorescence light emitted by the excited fluorescent entities in the sample is registered after each pulse of the excitation light (3) and overlapping with applying the de-excitation light (13) with high temporal resolution between consecutive pulses of the excitation light (3).