Human cloning has been a hot topic ever since Dolly the sheep was cloned in 1997. A subject of great debate around the world, the idea of producing children who are genetically virtually identical to pre-existing individuals seems unethical to some, while others see the possibility to do good for infertile couples and the broader society. Many nations have outlawed the process, but the isolation in 1998 of human embryonic stem cells has further muddied the waters, since stem cells derived from cloned human embryos are useful for studying various genetic diseases and developing unique therapies. While improper cloning can cause deleterious side effects, there is no scientific basis for associating these side effects with the death date of the cloned individual. Furthermore, environment plays such a substantial role in a person's development that any clones could be expected to be substantially different in both personality and appearance.