  Recently, laser cooling methods have been extended from atoms to molecules.
The complex rotational and vibrational energy level structure of molecules
makes laser cooling difficult, but these difficulties have been overcome and
molecules have now been cooled to a few microkelvin and trapped for several
seconds. This opens many possibilities for applications in quantum science and
technology, controlled chemistry, and tests of fundamental physics. This
article explains how molecules can be decelerated, cooled and trapped using
laser light, reviews the progress made in recent years, and outlines some
future applications.
