There’s unexpected movement in the world of cell biology — specifically, with the energy factories known as mitochondria.Ever since they were discovered in the mid-nineteenth century, mitochondria have been known as organelles that reside inside cells. But that textbook picture now seems to be wrong. An explosion of research is challenging mitochondria’s long-standing image as exclusively cellular organelles. “They may be a multicellular organelle,” says Jonathan Brestoff, an immunologist who st...