The (name of the) first mammal to be created by cloning a cell from an adult animal. In this particular case, the cell came from the mammary tissue of an adult ewe. The creation of Dolly showed that the process of differentiation into adult tissue is not, as previously thought, irreversible. The result was achieved by nuclear transfer (q.v.). Dolly's birth was announced in 1997. Since then, cattle and mice have also been cloned from adult cells.