Junying Yu, James Thomson and Shinya Yamanaka

A fierce moral debate—whether the therapeutic potential of stem cells could justify destroying embryos to get them—appeared to vanish when scientists in Wisconsin and Japan announced that they had figured out how to convert adult skin cells into near-perfect copies of the wonder cells. More research remains to be done, but this might be the most delightful discovery since common bread mold birthed the age of antibiotics.