Zhong Zhong was the first primate cloned using somatic cell nuclear transfer.
Zhong Zhong was one of two crab-eating macaques produced by Chinese researchers using somatic cell nuclear transfer, or SCNT. Hua Hua, born shortly afterward, was the second clone. The pair were announced in 2018 as the first primates successfully produced with the same basic cloning method used to create Dolly the sheep.
SCNT involves removing the nucleus from an egg cell and replacing it with the nucleus of a body cell. The reconstructed egg is then stimulated to begin embryonic development and implanted into a surrogate. Reprogramming a transferred nucleus proved particularly difficult in primates, making the macaque births a major technical milestone.
Zhong Zhong was born on November 27, 2017, and Hua Hua followed on December 5. They are sometimes confused with Tetra, a rhesus macaque created by embryo splitting in 1999; Tetra was an earlier cloned primate, but not an SCNT clone. Dolly was a sheep, not a primate.