The first, largest and most-successful panda-breeding center in the world is China's Research and Conservation Centre at Wolong.

You You, the last panda to give birth this season, has twins but the second is stillborn.

A 4-year-old panda travels from San Diego to China; 14 panda cubs are separated from their mothers in an official ceremony.

The spring mating season begins and the pressure is on to reproduce; the behavior of wild pandas in China's Qinling Mountains.

Revisiting some of the cubs as they have grown from newborns to adolescents; the year's successes and failures.