Which internal organ in Humans regenerates?

It’s Liver. Liver is the only internal organ of human beings which is capable of regeneration of lost tissues. Minimum 25% of the liver can regenerate into the whole liver.
This is because the hepatocytes in liver reenter the cell cycle which is a series of events that takes place in a cell leading to its division and duplication (replication). The regeneration of activated by the p75 receptors. The regeneration of Liver is known since ancient Greeks time. A mythological story about Prometheus , who was bound to a rock as a punishment from Zeus and a great eagle ate his liver every day only to have it grow back to be eaten again the next day. However, the speed of regeneration is not that much.