1996: Dolly the sheep is born. It is the first mammal cloned from an adult.
2001: American scientists announce the first cloned human embryos, but the research is not validated.
2004: South Korean researchers announce the first cloned human embryos from cells of an adult.
2005: South Koreans announce first embryonic stem cell lines from cloned human embryos, but later admit the reports contained serious errors.
2006: Korean research shown to be fraudulent, and the studies are retracted.
2007: Reports of first cloned embryos of macaque monkeys, then of the first embryonic stem cells derived from human skin cells by genetic engineering.
2008: Stemagen claims to be first research team to grow cloned embryonic cells to the blastocyst stage, but fails to go the next step and harvest stem cells. The blastocyst is a structure in early embryonic development that contains a cluster of cells from which the embryo arises.