In mouse hair follicles, pigment cells in the hair germ area actively make new pigment cells and stem cells, while those in the bulge stay quiet and only make more stem cells.

When mouse hair is repeatedly plucked, more pigment cells get stuck in the bulge area (from 10% to 50% of follicles), and these stuck cells don't help make new hair color.

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

Mouse pigment stem cells don't have a special group that never changes; different cells make Oca2 protein in each hair growth cycle.

When stress triggers a chemical called norepinephrine, it can permanently wipe out the stem cells that give hair its color, so once they're gone, your hair can't naturally regain its color.

Mouse hair pigment cells move between different parts of the hair follicle and change their state back and forth, which is linked to WNT signaling.