During chemical reactions, atoms and molecules regroup and form new constellations. Chemical reactions are affected by heat and light, among other things. The sequence of events can proceed very quickly. At the end of the 1940s, Ronald Norrish and George Porter built an extremely powerful lamp that emitted very short bursts of light. The light's energy triggered reactions among the molecules or split them into parts that were inclined to react. By registering the light spectrums that are characteristic for different substances, the progress of the reaction could be monitored.