Yoichiro Nambu of the U.S. and Japan's Makoto Kobayashi and Toshihide Maskawa won the 2008 Nobel Prize in physics for reaching on symmetry at the microscopic level, the Nobel committee announced Tuesday.

Nambu from the University of Chicago was awarded "for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics," the committee said.

Meanwhile, Kobayashi and Maskawa were honored "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature," it added.

"Nambu's theories permeate the standard model of elementary particle physics. The model unifies the smallest building blocks of all matter and three of nature's four forces in one single theory," said Royal Swedish Academy of Sciences in the citation.

It added Kobayashi and Maskawa "explained broken symmetry within the framework of the standard model but required that the model be extended to three families of quarks."

As early as 1960, Nambu formulated his mathematical description of spontaneous broken symmetry in elementary particle physics and his theories permeate the standard model of elementary particle physics.

Nambu, born 1921 in Tokyo, is a professor emeritus at the Enrico Fermi Institute at the University of Chicago.

He won half the award, while Kobayashi and Maskawa shared the other half. The trio will together share the 10 million kronor (about 1.42 million U.S. dollars) purse, a diploma and an invitation to the prize ceremonies in Stockholm on Dec. 10.

Kobayashi, 64, is a professor emeritus at the High Energy Accelerator Research Organisation in Tsukuba, while Maskawa, 68, holds the same title at the Yukawa institute for Theoretical Physics at Kyoto University.

In the 1970s, Kobayashi and Maskawa described the spontaneous broken symmetries in a way differed from Nambu.

This was the second of this year's crop of Nobel prizes, which are handed out annually for achievements in science, literature, economics and peace.

All but one of the prizes were established in the will of 19th century dynamite millionaire Alfred Nobel. The economics award was established by Sweden's central bank in 1968.

On Monday, the Nobel Medicine Prize went to France's Francoise Barre-Sinoussi and Luc Montagnier, and Harald zur Hausen of Germany for their "discoveries of two viruses causing severe human diseases."

Nobel died childless and dedicated his vast fortune to create "prizes for those, who, during the preceding year, shall have conferred the greatest benefit on mankind."

The prizes have been awarded since 1901. Each prize consists of a medal, a personal diploma and a cash award of 10 million Swedish kronor(1.42 million U.S. dollars).