A subset of experimental physics, dedicated to the examination of phenomena at temperatures lower than room-temperature. The extent of the regime of "low temperature" is a rather gray area, but is generally understood to encompass "lower-than-rom temperature" phenomena like ice formation (and it's associated amorphous solid water), as well as "extreme" low temperature phenomena, such as the Meissner Effect, in the low-temperature limit of a superconducting substance, ofen exhibited at liquid helium temperatures.