ITER announced this week that the Central Solenoid—the world’s most powerful magnet and beating heart of the tokamak—is finally complete, and will begin assembly soon. At the heart of this engineering miracle is a 3,000-ton magnet system central to creating an “invisible shield” that keeps superheated plasma contained long enough to kickstart a fusion reaction. Once assembled, this solenoid will be the world’s most powerful magnet. It will be contained inside an “exoskeleton”—made of 9,000 individual parts from eight U.S. suppliers—which will support the Central Solenoid as it generates extreme forces capable of kickstarting a fusion reaction. However, that’s still a long ways off, as recent ITER estimates place the reactor’s first plasma date at around 2035.