Your body's blood-making stem cells, hematopoietic stem cells (HSC), are like factory managers who work best when calm and rested. But when stress hits, like infection or injury, they spring into action, churning out immune cells to defend you. Over time, too much stress wears them down, making them age faster and lose their spark. Continue Reading Category:Space, Science Tags:interstellar space, Astronauts, Stem Cells
