On August 26, 2025, the Jiangmen Underground Neutrino Observatory (JUNO) successfully completed the filling of 20,000 tonnes of liquid scintillator and began formal data collection. Located 700 meters underground in Guangdong, southern China, this massive facility is now the world's first ultra-large, ultra-precision neutrino experiment. Initial data shows its performance exceeds design expectations. This milestone allows scientists to tackle one of the biggest questions in particle physics: determining the neutrino mass ordering. It will also enable cutting-edge research on neutrinos originating from the sun, supernovae, the atmosphere and Earth. A new window into the universe has opened! (CGTN)