Cooling matter is not easy. Atoms and molecules have the tendency to jump around, to rotate and to vibrate. Freezing these particles by slowing them down is a complicated process. For individual atoms, physicists have figured out over the years how to carry out this cooling process, using techniques like laser cooling, where finely tuned lasers remove energy from the particles. Molecules, on the other hand, are much harder to cool down so that they stand still. These particles consist of two or more atoms that are bound together, and as compound particles they are able to jiggle around in many more ways.