In February 1997, newspapers around the world reported the birth in Edinburgh, Scotland, of a lamb named Dolly. Such an event would not normally be considered newsworthy. Even the fact that Dolly had an identical twin would not typically have added much to the story. But the event was truly a landmark in science, because this lamb was not born in the usual way. Rather than being the product of a sperm and an egg from two parents, Dolly came into existence when the genetic material from an adult sheep was transplanted into a cell that developed into an exact copy of that sheep. For the moment, most scientists are talking about relatively non-controversial applications of the technology – such as cloning cows that are especially good milk producers. It is undoubtedly just a matter of time before the technology is in place to create copies of other humans from the DNA in the nucleus of a single cell. Consider the potential benefits to society. We could make perfect, but younger, copies of brilliant scientists, surgeons, or even chefs. Infertile couples could be helped to bear children, and genetic diseases could perhaps be cured or prevented by manipulating the structure of the genes causing them. The extraordinary birth of a lamb named Dolly serves as an appropriate entry into the relatively new and fascinating world of human genetics.