Inside the underground lab in China tasked with solving a physics mystery

A giant sphere 700 meters (2,300 feet) underground with thousands of light-detecting tubes will be sealed in a 12-story cylindrical pool of water in coming months for an experiment that will shine new light on elusive subatomic particles known as neutrinos.

After years of construction, the $300 million Jiangmen Underground Neutrino Observatory (JUNO) in China’s southern Guangdong province will soon start gathering data on neutrinos, a product of nuclear reactions, to help solve one of the biggest mysteries in particle physics.

Every second, trillions of extremely small neutrinos pass through matter, including the human body.