Your hair color depends on special stem cells in your hair roots, and long-term stress from inflammation or oxidation can mess them up, making them disappear or mature too soon.

As we age, the stem cells that give color to our hair can start acting up — they might turn into pigment cells too soon or in the wrong place, which could be why our hair turns gray.

When your hair grows fast, it might stress the cells that give hair its color, causing them to wear out faster and turn hair gray sooner.

When mouse hair starts growing, pigment stem cells in the hair germ turn on color-making and branch-related genes before they divide.

As we get older, the cells that give hair its color start to die off because of stress and lower levels of a protective protein, which is why hair turns gray and doesn’t grow back colored.

Going gray might happen because the stem cells that keep your hair colored stop working properly as you age, according to studies in people and specially tagged mice.