The liver is the only internal organ in the human body capable of repairing and regenerating itself after damage. However, long-term damage such as chronic liver disease reduces this ability, creating serious health problems. Currently, the only available treatment is a transplant. Researchers are using stem cells to understand the regenerative capacity of the liver. Tissue engineers are investigating whether stem cells can be used to create liver cells and tissue for transplant, or whether immune cells can be reprogrammed to remove damaged liver tissue.