There are only two fundamental opportunities in the history ofthermodynamics.They are the establishment of classical therniodynamics for only spontaneous process in simple system on the basis of Carnot theorem and the establishment of modern thermodynamics for nonspontaneous process in coupled system on the basis ofthe thermodynamic couplingtheory, since there are only two kinds of spontaneous processes and nonspontaneous processes of macroscopic changes inNature (excluding unknown parts of the universe). Thermodynamics is a core part of modern science, and the second law of thermodynamics is the core of thermodynamics, which was stagnated for about 150 years in its classical stage only for spontaneous process in simple systems. The second law of thermodynamics shows the change in direction of the macroscopic world (or calledthe arrow of time ), and is regarded as one of greatest ten equations in history.