Cell biology. Beyond clotting: the powers of platelets.

Platelets not only save us from bleeding to death, but in recent years, platelets have also displayed powers no one imagined they had. They are healers that pour out growth factors and other soothing molecules that help damaged tissue rebuild. They are soldiers that spark the protective response known as inflammation, alert immune cells, and even attack microbial interlopers. They are long-haul truckers that pick up and deliver chemicals such as serotonin, which helps the liver regenerate after injury. They are even engineers, shaping the vascular system in newborns. Additional platelet functions continue to come to light, and biologists have just described a novel way that the body might make these multitalented cells—a finding that could one day ease the demand for donated blood.