STOCKHOLM, Sweden — Two Japanese citizens and an American won the 2008 Nobel Prize in physics for discoveries that help explain the behavior of the smallest particles of matter.

American Yoichiro Nambu, 87, of the University of Chicago, won half of the $1.4 million prize for the discovery of a mechanism called spontaneous broken symmetry.

Makoto Kobayashi and Toshihide Maskawa of Japan shared the other half of the prize for discovering the origin of the broken symmetry that predicted the existence of at least three families of quarks in nature.

The academy said the trio "presented theoretical insights that give us a deeper understanding of what happens far inside the tiniest building blocks of matter."