Zhong Zhong and Hua Hua are the first cloned primates produced by this technique. When other scientists tried to clone monkeys before this, they used donated embryonic stem cells, but Zhong Zhong and Hua Hua came from donated nuclei from fetal cells, which is harder to do. The two baby monkeys were both born at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai.