China is finishing construction on its $300 million physics research facility located 700 meters underground in rural Guangdong province. The Jiangmen Underground Neutrino Observatory (JUNO) has been under construction for 10 years, and in a few months will be sealed off for the next 30 years as it runs experiments and collects data. JUNO aims to determine which types of neutrinos, which are tiny subatomic particles, have the greatest mass. Neutrinos can pass through normal objects unimpeded and undetected, making them incredibly difficult to research. About 100 trillion neutrinos pass through the human body every second, according to IceCube Neutrino Observatory research facility at the South Pole in Antartica.REUTERS VIDEO