This lecture covers the thermodynamics of irreversible processes, generalized currents and forces, Onsager matrix, Onsager reciprocity relations, Ohm's law, Hall effect, Seebeck effect, Nernst effect, Ettingshausen effect, Righi-Leduc effect, spin diffusion length, GMR, spin accumulation, spin interface resistance, heat-driven spin torque in insulator, and spin current in magnetic metals.