stem cell potency

Potency is a measure of how many different cell types a given stem cell is able to become — its range of possible destinations. Not all stem cells are equally versatile: some can turn into almost anything, while others are limited to a small handful of related types. Think of potency as how broad a menu a cell can order from. The earlier and more unspecialized the cell, the longer its menu; the more committed it already is, the shorter.

Biologists arrange potency as a descending ladder. At the top sits totipotency, the power to make every cell of a body plus the supporting tissues of a pregnancy, such as the placenta — only the freshly fertilized egg and its first few divisions qualify. Next is pluripotency: the ability to become any cell type of the body itself, but not a whole organism. Below that is multipotency, limited to a related family of types, such as the various kinds of blood cell. At the bottom is unipotency, which yields just one type.

This ladder matters because it predicts what a cell can and cannot do, and it generally runs one way: as cells develop, they step down the rungs, trading breadth for a settled identity. Knowing a cell's rung tells a researcher whether it could, in principle, rebuild many tissues or only refresh one. Much of stem cell science is about reading, preserving, or deliberately winding back a cell's position on this ladder.