STOCKHOLM -- Japan's Makoto Kobayashi and Toshihide Maskawa, and Yoichiro Nambu of the United States won the Nobel Physics Prize Tuesday for pioneering work on fundamental particles of matter called quarks.

Nambu won half the prize for developing a "standard model of elementary particle physics [which] unifies the smallest building blocks of all matter and three of nature's four forces in one single theory," the Nobel jury said.

The Japanese duo was honored for their discovery "of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature."