Takaaki Kajita, director of the University of Tokyo's Institute for Cosmic Ray Research, gestures during a news conference in Tokyo October 6, 2015. Kajita and Canadian scientist Arthur McDonald won the 2015 Nobel Prize for Physics on Tuesday for discovering that elusive subatomic particles called neutrinos have mass, opening a new window onto the fundamental nature of the universe. [Photo/Agencies]

Takaaki Kajita of Japan and Arthur McDonald of Canada won the Nobel Prize in physics on Tuesday for discovering the "chameleon-like" nature of neutrinos, work that yielded the crucial insight that the tiny particles have mass.

The Royal Swedish Academy of Sciences said the two researchers had made key contributions to experiments showing that neutrinos change identities as they whiz through the universe at nearly the speed of light.

Neutrinos are miniscule particles created in nuclear reactions, such as in the sun and the stars, or in nuclear power plants. There are three kinds of neutrinos and the laureates showed they oscillate from one kind to another, dispelling the long-held notion that they were massless.

"The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe," the academy said.

Kajita, 56, is director of the Institute for Cosmic Ray Research and professor at the University of Tokyo. McDonald, 72, is a professor emeritus at Queen's University in Kingston, Canada.

The winners will split the 8 million Swedish kronor (about $960,000) prize money. Each winner also gets a diploma and a gold medal at the prize ceremony on Dec 10.

Kajita and McDonald made their discoveries while working at the Super-Kamiokande detector in Japan and Sudbury Neutrino Observatory in Canada, respectively.

Kajita showed in 1998 that neutrinos captured at the detector underwent a metamorphosis in the atmosphere, the academy said. Three years later McDonald found that neutrinos coming from the sun also switched identities.