Controlled nuclear fusion of deuterium-tritium is a power source that is friendly to Earth’s biosphere. The 27 EU member countries and 6 more nations actively invest on the research and development of a commercial and fully functional nuclear fusion reactor of TOKAMAK design. The associated research community proceeded since 2010 on the construction of the biggest TOKAMAK in southern France with the name ITER. ITER will be a crucial experiment to produce power with means of controlled fusion of hydrogen plasmas. In this talk, the topology of the confining magnetic field will be presented. Then, technologies employed on the reactor for its successful outcome are presented. There will be also a brief description of the most important diagnostic setups that promote the research on the physics of high temperature plasmas.