Researchers at Newcastle University in England report they have coaxed the first human sperm cells from embryonic stem cells, in a remarkable demonstration of how quickly the field of stem-cell ...

We all know the drill for reproduction—sperm meets egg. But mice aren’t people. And the same recipe doesn’t work for human reproductive cells. One reason, according to Dr. Mitinori Saitou at Kyoto ...

Almost every type of human cell is powered by mitochondria, bean-shaped organelles that use oxygen to synthesize usable energy.* These structures evolved billions of years ago from free-swimming ...