Abstract. An overview of the energy problem in the world is presented. The colossal task of 'decarbonizing' the current energy system, with ~85% of the primary energy produced from fossil sources is discussed. There are at the moment only two options that can contribute to a solution: renewable energy (sun, wind, hydro, etc.) or nuclear fi ssion. Their contributions, ~2% for sun and wind, ~6% for hydro and ~5% for fi ssion, will need to be enormously increased in a relatively short time, to meet the targets set by policy makers. The possible role and large potential for fusion to contribute to a solution in the future as a safe, nearly inexhaustible and environmentally compatible energy source is discussed. The principles of magnetic and inertial confi nement are outlined, and the two main options for magnetic confi nement, tokamak and stellarator, are explained. The status of magnetic fusion is summarized and the next steps in fusion research, ITER and DEMO, briefl y presented.