Fusion energy just took a real step forward in Japan: JT-60SA, the largest experimental fusion reactor on Earth, has officially powered up in Ibaraki Prefecture. Standing six stories tall, it heats plasma to roughly 200 million degrees Celsius — hotter than the sun’s core — to study the same process that lights the stars. More than 500 scientists and 70 companies across Japan and the European Union built it together, and its job is to pave the way for ITER, the even larger reactor rising in France. Fusion still has a long road ahead, but moments like this remind us what becomes possible when nations pool decades of expertise toward a shared, emissions-free future.