Here’s what you’ll learn when you read this story:A study links graying hair to stem cells getting stuck, unable to color new hair growth. If only our pesky stem cells didn’t get stuck in place after a while, maybe we wouldn’t have gray hair. In a study in the journal Nature, researchers from New York University’s Grossman School of Medicine revealed how stuck melanocyte stem cells (McSCs) can’t make the protein needed to pigment hair, potentially explaining gray hair. “The newfound mechanisms raise the possibility that the same fixed positioning of melanocyte stem cells may exist in humans. And while stress has also been associated with graying hair, unrelated Harvard research says that stress simply increases the hair regrowth pattern, speeding up the aging process for hair follicles.