LOS ANGELES, Dec. 22 (Xinhua) -- Zhen Zhen, the newest charismatic baby panda went on display on Saturday at the San Diego Zoo, about 80 miles (about 108 kilometers) south of Los Angeles, zoo officials said.

    Since birth four months ago, the panda had been visible only on the zoo's website.

The 20-week-old giant panda cub Zhen Zhen is photographed in San Diego on Dec. 21, 2007. San Diego Zoo visitors will be able to see the 20-week-old giant panda cub for the first time when Zhen Zhen makes her debut on Saturday, Dec. 22, 2007. (Xinhua/Reuters Photo) Photo Gallery>>>

    Only four U.S. zoos have pandas: San Diego, Memphis, Atlanta and the National Zoo in Washington and D.C. San Diego has the most pandas, with four.

    There are many small things not known about pandas, but there is one large thing that is well-documented: Giant pandas are the most popular animals ever displayed in U.S. zoos.

    Under a complex loan agreement with the Chinese government, Zhen Zhen, born in August at the zoo, will someday go to live in China. But that day is years away.

    Kathy Hawk, the San Diego Zoo's senior panda keeper, has tended to all the pandas, the adults shipped from China and the four cubs born here. Under the agreement, China retains the rights to any cubs born at the San Diego Zoo, and they must be sent to their ancestral home after three years.

    "Zhen Zhen is very reminiscent of Hua Mei," Hawk said. "She's definitely a show-stopper."

    To the panda constituency, a comparison to Hua Mei is the gold standard. Born at the zoo in 1999, she was an instant favorite.

    Her departure to China in 2004 occasioned much local sorrow. Fans still besiege the zoo for updates. A male cub also had been sent to China.

    At 17 pounds, Zhen Zhen is heavier than the other three cubs born at the zoo were at her age. For another year, her nourishment will be from nursing off of 220-pound Bai Yun, the mother.

    At the beginning, Zhen Zhen will be out for viewing only from 9a.m. to 11 a.m. As the cub gets more comfortable with crowds and picture-taking, the hours might be extended.

    Zhen Zhen's debut has been much anticipated, as comments on the zoo's panda blog attest.

    Although Zhen Zhen is the latest attraction, the other pandas --the adult male Gao Gao and young female Su Lin -- have their own followings.