Quantum thermodynamics addresses the emergence of thermodynamic phenomena from quantum mechanics. In addition, it aims at clarifying to what extent the paradigms of thermodynamics apply in the quantum domain when quantum effects such as quantum correlations, quantum fluctuations, coherences and entanglement, come into play. Emerging novel quantum technologies motivate the quest for smaller devices and quantum thermal machines. Such devices operating at the quantum level form the foundation for quantum information processing, quantum sensing and metrology.