FLIM composite image series were acquired to reveal regularities in the progression of cellular damage to determine a plausible mechanism of glioma cell death induced by hypericin PDT. FLIM image acquisition and hypericin PDT are simultaneously initiated by the excitation laser and image sequences are recorded for single glioma cells. The first step is to locate a cell of interest and to determine suitable acquisition parameters with a low irradiance of around 1 μW/μm 2 , which was found to not cause significant photodamage to the cells. For image acquisition, the irradiance is increased to initiate PDT while simultaneously acquiring time-resolved PL data. The irradiance was adjusted to 7-10 μW/μm 2 , which is low enough to cause a slowly proceeding cell damage and thus to enable the visualization of the PDT progression over the course of multiple images (which are labeled M1 … M8). The acquisition and analysis principles of FLIM images presented in this work are given in section 3 of the SI. Fig. shows the progression of PDT for a single glioma cell incubated with hypericin and resorufin displaying individual stages of cellular damage.