The 2015 Nobel Prize in Physics has been won by Takaaki Kajita and Arthur McDonald, for discovering how neutrinos switch between different “flavours,” the BBC reports.

Neutrinos are ubiquitous subatomic particles with almost no mass and which rarely interact with anything else, making them very difficult to study.

Kajita and McDonald made important measurements of their properties using huge instruments in Japan and Canada.

They were named at a press conference in Sweden.

Goran Hansson, secretary general of the Royal Swedish Academy of Sciences, which decides on the award, declared: “This year’s prize is about changes of identity among some of the most abundant inhabitants of the universe.”