stem cell

A stem cell is an unspecialized cell that has not yet decided what it will become. Most cells in your body have a fixed job — a heart cell beats, a skin cell forms a barrier — but a stem cell sits one step earlier, still blank and full of options. Think of it as fresh modeling clay that has not yet been shaped, kept in reserve by the body so there is always raw material on hand.

Stem cells are defined by two powers that other cells lack. The first is self-renewal: when a stem cell divides, it can make a copy of itself, so the supply never runs dry. The second is differentiation: it can also mature into a specialized cell type, taking on a permanent job. By balancing these two — copying itself while also producing specialists — a small pool of stem cells can both maintain itself and continuously rebuild tissue.

This makes stem cells the body's repair reservoir. They quietly replace the skin, blood, and gut lining cells you shed every day, and they help mend injuries. Because they can become so many things, they are also the central tool of regenerative medicine, which aims to use them to repair tissue the body cannot heal on its own — though turning that promise into proven, safe therapy is still difficult and far from finished.