Although the in situ immunofluorescence has been extensively utilized for the detection of single/simple DNA damage including one type of lesions , the simultaneous detection of DSBs and non-DSB lesions has been reported only in a few studies . The difficulty in achieving visualization of base lesions, in terms of foci, lies in the fact that only a few molecules of every specific DNA repair protein (e.g., OGG1, NTH1, APE1 etc.) are taking part in the repair of a single lesion, in contrast with DSB repair where hundreds/thousands of molecules of the same DNA repair protein (like γH2AX/53BP1) may contribute to the process, as discussed above. Moreover, unlike γH2AX protein which becomes present mainly upon a DSB formation, most of the non-DSB repair proteins have endogenous concentrations within the cell nucleus, therefore resulting in increased background signal. A pre-extraction step in the experimental procedure, as well as the introduction of the Pclc colocalization parameter in image analysis  have helped researchers overcome these obstacles (Figure 1). In Figure 1, the theoretical description of the Pclc-parameter is given in detail (panel A), along with its application for the detection of complex DNA damage (panel B) and an additional application for the derivation of useful data regarding the localization of DNA repair proteins in euchromatin/heterochromatin regions (panel C).