The possibility of employing strong optical and x-ray laser fields to investigate processes in the realm of classical and quantum electrodynamics as well as nuclear quantum optics is considered. In the first part we show on the theoretical side how modern strong optical laser fields can be employed to test the fundamental classical equations of motion of the electron which include radiation reaction, i.e., the effect of the radiation emitted by the electron on its own motion. Then, we clarify the quantum origin of radiation reaction and discuss a new radiation regime where both quantum and radiation effects dominate the electron dynamics. The second part is dedicated to the possibility of controlling nuclear transitions with coherent x-ray light. In particular, we investigate the resonant driving of nuclear transitions by super-intense x-ray laser fields considering parameters of upcoming high-frequency coherent light sources. As relevant application, the controlled pumping or release of energy stored in long-lived nuclear states is discussed.