Adult stem cells

Adult stem cells are undifferentiated cells that exist throughout the human body. They can divide to replenish dying cells, and also regenerate to repair damaged tissues. An example are olfactory cells in the nasal passages, which replenish to restore the sense of smell after suffering a cold.

Researchers have shown that adult stem cells from one germ layer can be converted into those of another, making adult stem cells at least as useful for cures as embryonic stem cells might be. For example, adult stems have been able to turn marrow cells into heart muscle and blood vessels in humans.