(CNN)Here's some background information about cloning, a process of creating an identical copy of an original.
Reproductive Cloning is the process of making a full living copy of an organism. Reproductive cloning of animals transplants nuclei from body cells into eggs that have had their nucleus removed. That egg is then stimulated to divide using an electrical charge and is implanted into the uterus of a female.
1952 - Scientists demonstrate they can remove the nucleus from a frog's egg, replace it with the nucleus of an embryonic frog cell, and get the egg to develop into a tadpole.