In 1995 and 1996, researchers at the Roslin Institute in Edinburgh, Scotland, cloned mammals for the first time. Keith Campbell, Jim McWhir, William Ritchie, and Ian Wilmut cloned two sheep, Megan and Morag, using sheep embryo cells. The experiments indicated how to reprogram nuclei from differentiated cells to produce live offspring, and that a single population of differentiated cells could produce multiple offspring. They reported their results in the article 'Sheep Cloned by Nuclear Transfer from a Cultured Cell Line' in March 1996. This experiment led the Roslin team to later clone mammals from adult body cells and to genetically engineer mammals.

In the 1990s, Ian Wilmut, Jim McWhir, and Keith Campbell performed experiments while working at the Roslin Institute in Roslin, Scotland. Wilmut, McWhir, and Campbell collaborated with Angelica Schnieke and Alex J. Kind at PPL Therapeutics in Roslin, a company researching cloning and genetic manipulation for livestock. Their experiments resulted in several sheep being born in July 1996, one of which was a sheep named Dolly born 5 July 1996. Dolly was the first sheep cloned and developed from the nuclei of fully differentiated adult cells, rather than from the nuclei of early embryonic cells. They published their results in Viable Offspring Derived from Fetal and Adult Mammalian Cells (abbreviated Viable Offspring) on 27 February 1997.

In 2015, Revive & Restore launched the Woolly Mammoth Revival Project with a goal of engineering a creature with genes from the woolly mammoth and introducing it back into the tundra to combat climate change. Revive & Restore is a nonprofit in California that uses genome editing technologies to enhance conservation efforts in sometimes controversial ways. In order to de-extinct the woolly mammoth, researchers theorize that they can manipulate the genome of the Asian elephant, which is the mammoth’s closest living evolutionary relative, to make it resemble the genome of the extinct woolly mammoth. While their goal is to create a new elephant-mammoth hybrid species, or a mammophant, that looks and functions like the extinct woolly mammoth, critics have suggested researchers involved in the project have misled and exaggerated the process. As of 2021, researchers have not yet succeeded in their efforts to de-extinct the woolly mammoth, but have expressed that it may become a reality within a decade.

In 1962 researcher John Bertrand Gurdon at the University of Oxford in Oxford, England, conducted a series of experiments on the developmental capacity of nuclei taken from intestinal epithelium cells of feeding tadpoles. In the experiments, Gurdon conducted nuclear transplantation, or cloning, of differentiated cells, or cells that have already specialized to become one cell type or another, in tadpoles. Gurdon's experiment showed that differentiated adult cells could be induced to an undifferentiated state, where they could once again become multiple cell types. Gurdon's experiment disproved the theory that differentiated cells could not be undifferentiated or dedifferentiated into a new type of differentiated cell. Gurdon's experiment demonstrated nuclear transplantation, also called cloning, using differentiated cells.