Cryogenic treating is freezing a part with liquid nitrogen or helium to bring it down as close to the liquid temperature of the element you're using as possible and then allowing the part to return slowly back to ambient temperature. The basic result is that the molecular structure tightens as the item is frozen, and stays tight as it's brought back to it's normal temperature, so that the item is, in fact, stronger than it was originally. This is especially useful on parts that don't have maybe the right design or alloy construction for high output applications from the factory, such as transmission parts, crankshafts, connecting rods, and anything else that you want to make sure the internal structure is as strong as it possibly can be.