Pump-probe experiments are a technique used in physics and chemistry to study fast processes at the molecular or atomic level. In these experiments, a short pulse of light, called the "pump," excites a sample, initiating a reaction or change. A second pulse, known as the "probe," follows shortly after to measure the effects of the initial excitation. These experiments allow scientists to capture dynamic events, such as chemical reactions or electron movements, in real-time. By analyzing the changes in the probe signal, researchers can gain insights into the mechanisms of processes like photosynthesis or electron transfer in molecular systems.