Ultrafast techniques refer to methods used to study processes that occur on extremely short timescales, typically in the range of femtoseconds (10^-15 seconds) to picoseconds (10^-12 seconds). These techniques allow scientists to observe rapid phenomena, such as chemical reactions and electron movements, providing insights into the fundamental behavior of matter at the atomic and molecular levels. One of the most common ultrafast techniques is pump-probe spectroscopy, which involves using a short laser pulse to initiate a reaction and a second pulse to probe the system at various time intervals. This approach has applications in fields like chemistry, physics, and materials science, enabling researchers to capture dynamic processes that were previously impossible to observe.