Intracellular molecular transport and localization are crucial for cells (plant cells as much as mammalian cells) to proliferate and to adapt to diverse environmental conditions. Here, some aspects of the microscopy-based method of fluorescence recovery after photobleaching (FRAP) are introduced. In the course of the last years, this has become a very powerful tool to study dynamic processes in living cells and tissue, and it is expected to experience further increasing demand because quantitative information on biological systems becomes more and more important. This review introduces the FRAP methodology, including some theoretical background, describes challenges and pitfalls, and presents some recent advanced applications.