Illustration showing the cloning of Dolly the sheep (left) and possibilities for human cloning (right). Dolly was the first mammal to be cloned from an adult cell. The nucleus from an adult udder cell was injected into an egg cell that had had its nucleus removed. A spark of electricity was used to fuse the udder nucleus with the egg cytoplasm and stimulated the egg to grow into an embryo. The embryo was implanted into the womb of a surrogate sheep. Dolly was born in July 1996. Similar techniques could be used to create cloned human tissues.