FRAP (Fluorescence Recovery After Photobleaching), or fluorescence recovery after photobleaching, is one of the popular fluorescence imaging methods for studying dynamic processes in cell and molecular biology, especially for protein interactions. With this technique, the 2D or 3D mobility of fluorescently labelled molecules inside living cells can be measured(live cell imaging). The principle is based on the exposure of the region of interest(ROI) to an intense laser beam (photobleaching), whereby irreversible fluorophoreillumination occurs and subsequent fluorescence recovery in the bleached regions due to diffusive exchange with non-bleached fluorophore molecules. This process makes it possible to identify the type of transport process - by distinguishing simple diffusion from systematic movement, its rate can be determined and the proportion of mobile molecules can be determined.