The TCSPC histograms of the individual dyes and the fits thereof are displayed in section 2 of the SI. Fig. shows an exemplary FLIM composite image, which is the superposition of a photoluminescence (PL) intensity image (gray in Fig. ) and a FLT image. In the final FLIM composite image, the FLT is represented by the color and the fluorescence intensity is given by the brightness. The black curve in Fig. presents the histogram of the photon arrival times for all pixels in the FLT image showing three maxima at the average lifetimes of the three fluorescent probes. Additionally, the histograms of the regions of interest (ROI) marked in Fig. are given in Fig. in the respective colors. This data shows that resorufin is mainly located outside the cell, hypericin is found within the cell and is enriched in the ER and a small amount of PI can already be detected inside the cell nucleus. The detection of the small amount of PI in this cell in the early stages of cell death with beginning membrane permeabilization is only possible due to the single molecule sensitivity of the employed confocal microscope.