When a certain gene called Bcl2 isn't working right in mice, the stem cells that give rise to hair color die off when hair follicles go dormant, but the actual color-making cells are fine—this leads to hair turning gray faster.

In mice, when a specific gene called Bcl2 isn't working, the stem cells that make pigment die off when the hair cycle pauses, but the mature pigment cells stay alive — showing that stem cells really rely on this gene to survive.

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.

As we get older, the stem cells that keep our hair colored might stop working properly because of problems in their internal repair system, and once they're gone, our hair turns gray for good.

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.

In mice with a broken Dguok gene, their hair turns gray because the stem cells that give color to hair disappear early, even before the color actually fades.