This course is intended to describe fundamentals in thermodynamics with an emphasis on processes and cycles. A brief introduction is given with a historical description of early liquefaction attempts of gases and the physics concepts relevant for thermodynamics are reviewed. Processes and thermodynamic cycles of large and small scale refrigerators/liquefiers including cryocoolers are described, followed by a brief discussion on the methods to reach temperatures below 2K. The course is primarily designed for beginners in the cryogenics field and suited for students and engineers new to the field.