The Law of Temperature Transformation: Despite the special theory of relativity was discovered about 120 years ago, how the temperature transforms in the theory remains unknown.This historical outstanding problem was initiated from the phenomenological thermodynamics point of view by the late giants such as Planck, Einstein, Pauli and Laue and also followed intensively by many other people until today. Here we resolve this outstanding problem by using a completely different approach: writing a partition function in terms of path integral in the imaginary time at a finite temperature, then perform Lorentz transformation directly on the partition function. The most disruptive change from zero T to a finite T is the existence of a reservoir which sets up the temperature and the chemical potential. Then the original bi-partite problem of the System + Observer at zero T becomes a trinity problem of the Reservoir + System + Observer at a finite T. It is the relative motion between the system and the reservoir which dictates the Law of Temperature Transformation. We also study the effects of a finite chemical potential and the low energy limit leading to condensed matter systems. Impacts on the thermodynamic zeroth to the third laws are given. Contrast to the Unruh effects for an accelerating observer are made. Possible implications on the temperature of a quantum black hole are hinted through the AdS/CFT correspondence. Feasible experimental detections of these effects in the condensed matter systems are analyzed.