  The last few years have seen rapid progress in the application of laser
cooling to molecules. In this review, we examine what kinds of molecules can be
laser cooled, how to design a suitable cooling scheme, and how the cooling can
be understood and modelled. We review recent work on laser slowing,
magneto-optical trapping, sub-Doppler cooling, and the confinement of molecules
in conservative traps, with a focus on the fundamental principles of each
technique. Finally, we explore some of the exciting applications of
laser-cooled molecules that should be accessible in the near term.
