Hans Spemann uses a salamander embryo to demonstrate that the cell nucleus directs cellular division. Ten years later, he proposes replacing the nucleus in an egg cell with the nucleus from another cell.
Robert Briggs and Thomas J. King extract the nucleus from the cell of an advanced frog embryo and insert it into a frog egg, that then undergoes division.
J. B. S. Haldane coins the term clone.
John Gurdon transplants the nuclei from frog embryo cells into unfertilized eggs, that develop into short-lived tadpoles. He later shows that transplanted nuclei revert to an embryonic state.
Louise Brown, the first baby conceived via in-vitro fertilization, is born. 1984 Steen Willadsen produces a live lamb from early sheep embryo cells in a process known as twinning. It is later used on other animals.