Cloning involves creating genetically identical organisms through artificial means. There are two main types of cloning: artificial embryo twinning, which splits an embryo into two, and somatic cell nuclear transfer, where the nucleus of an adult cell is transferred into an egg cell. In 1996, Dolly the sheep was the first mammal cloned from an adult cell using somatic cell nuclear transfer. Cloning may have medical benefits like organ transplants but also risks like developmental failures and depriving clones of individuality.