Chemists use lasers to study how molecules interact with light. In some cases, a chemist may want to know how a molecule reacts when a pulse of light is used to excite it. In other cases, lasers can be used to gain information about the structure of the molecule. One of the reasons lasers are good for these purposes is that they can provide pulsed light to gain information about how molecules are changing over time. Another is that many “tricks” exist for controlling and manipulating the wavelength of the light produced by a laser, making them versatile light sources.