Laser cooling of molecules

A recent progress on laser cooling of molecules is summarized. Since the development during the 1980s for atomic species, laser cooling has been the very beginning step to cool and trap atoms for frontier research on quantum simulations, quantum sensing and precision measurements. Despite the complex internal structures of molecules, laser cooling of molecules have been realized with the deepened understanding of molecular structures and interaction between light and molecules. The development of laser technology over the last decades has also been a great aid for the laser cooling of molecules because many lasers are necessary to successfully cool the molecules. A detailed principle and development of laser cooling of molecules as well as the current status of the field are reviewed to give an introduction to the growing field of ultracold molecular physics.