The second law of thermodynamics presupposes a clear-cut distinction between the controllable and uncontrollable degrees of freedom by means of macroscopic operations. The cutting-edge technologies in quantum information and nanoscience seem to require us to abondon such a working hypothesis in favor of the distinction between the accessible and inaccessible degrees of freedom. In this talk, I will speak about the fundamentals of such information thermodynamics together with the related new results on fluctuation theorems.