Fusion reactions. Fusion in nature. Future energy demands. Energy alternatives. Fusion history. Different approaches to fusion. The Lawson criterion. Breakeven, ignition. Quality parameters of the fusion plasma. Fusion reactor power balance and thermal stability. Heating of fusion plasmas. The Energy principle applied to different configurations. Tokamak stability; MHD and non-MHD modes. Resistive instabilities. Resistive wall modes and feedback control. Density and beta limits. Edge localized mode (ELM), multi-faceted asymmetric radiation from the edge (MARFE). Fishbones. Disruptions. Confinement modes and energy confinement scaling laws. Reversed shear scenarios. Characteristics of different magnetic confinement schemes. Spherical and compact tokamaks. RFP and stellarator stability. Reactor design and reactor studies. ITER design. Magnetized target fusion. Inertial fusion; direct and indirect drive, fast ignition, the large experiments NIF and LMJ. Safety and environmental aspects of fusion. Fusion research at KTH and at different experiments in the world.