Principles of cryogenic techniques and gas cooling. Isentropic and isenthalpic cooling. The properties of Helium isotopes: superfluidity and the condensates, Heat exchangers, expansion engines, cryocoolers, dilution refrigerators. Atomic and nuclear adiabatic demagnetization. Low temperature thermometry. Type I and type II superconductors. Magnetic properties of superconductors. London model and phenomenological Landau-Ginsburg equations. Weak superconductivity (Josephson effect and SQUIDs). Cuprates and other families of new superconductive materials. Low dimensional superconductivity.