Thermodynamics generally starts with several basic concepts and leads to different thermodynamics laws. A thermodynamic system is a quantity of matter, which is defined by its boundary. In this chapter after short review of thermodynamic laws, nanothermodynamic and thermodynamic properties of nanosized systems are presented. They are essential topics in nanosize engineering examples. Since it is necessary to know the energy transductions that occur between living organisms and cells, the biological thermodynamics is considered. At the end of this chapter the energy and exergy of the human body as an open thermodynamic system is analyzed and obtained results are discussed.