Time-correlated single photon counting (TCSPC) is a technique used to measure the time intervals between the arrival of single photons. It involves a light source that emits photons, which are then detected by a sensitive detector. The time of each photon’s arrival is recorded with high precision, allowing researchers to analyze the timing of events in various applications, such as fluorescence lifetime imaging. This method is particularly useful in fields like biophysics and quantum optics, where understanding the timing of photon emissions can provide insights into molecular interactions and the properties of materials. By correlating the arrival times of photons, scientists can create detailed temporal profiles of light emission, enhancing their understanding of complex systems.