During the twentieth and twenty-first centuries, Robert Paul Lanza studied embryonic stem cells, tissues, and endangered species as chief scientific officer of Advanced Cell Technology, Incorporated in Worcester, Massachusetts. Lanza's team cloned the endangered species of gaur Bos gaurus.

The Southern Gastric-Brooding Frog (Rheobatrachus silus) was an aquatic frog that lived in south-east Australia. In 2002, the International Union for Conservation of Nature Red List declared the frog extinct, although no wild specimens had been

Sir John Bertrand Gurdon further developed nuclear transplantation, the technique used to clone organisms and to create stem cells, while working in Britain in the second half of the twentieth century.

In 2007, the Human Fertilisation and Embryology Authority in London, UK, published "Hybrids and Chimeras: A Report on the Findings of the Consultation", which summarized a public debate about research on, and suggested policy for, human animal chimeras.

To educate its citizens about research into chimeras made from human and non-human animal cells, the United Kingdom's Human Fertilisation Embryology Authority published the consultation piece "Hybrids and Chimeras: A Consultation on the Ethical and Social Implications of Creating Human/Animal Embryos in Research," in 2007.

In the second half of the twentieth century, scientists learned how to clone some species of mammals. Scientists have applied somatic cell nuclear transfer to clone human and mammalian embryos as a means to produce stem cells for laboratory

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.

Dizhou Tong, also called Ti Chou Tung, studied marine animals and helped introduce and organize experimental embryology in China during the twentieth century. He introduced cellular nuclear transfer technology to the Chinese biological community, developed methods to clone organisms from many marine species, and investigated the role of cytoplasm in early development.

In the 1990s, researchers working at the Roslin Institute in Edinburgh, Scotland, performed cloning experiments in collaboration with PPL Therapeutics in Roslin, Scotland, on human coagulation factor IX, a protein.

In 2006, Kazutoshi Takahashi and Shinya Yamanaka reprogrammed mice fibroblast cells, which can produce only other fibroblast cells, t