TL;DR
Fusion, the power source that runs the Sun, has moved from physics labs onto construction sites. One company is finishing a 50-megawatt power plant it has promised to Microsoft for 2028, another has broken ground on a billion-dollar-scale campus in New Mexico, and Washington has just pledged $175 million for the parts that fire a fusion machine. What nobody has done yet is the one thing that matters: build a fusion machine that puts out more energy than it takes in. If someone does it in the next few years, cheap, carbon-free power on demand stops being a slogan and becomes an engineering schedule. If not, the plants going up now become very expensive experiments.
Below the line, for paid subscribers: The full story: where it stands, how we got here and what's dated next; our Odds board on 6 milestones, starting with "Commonwealth Fusion's SPARC machine makes its first plasma by 2027"; and every source.