Regeneration is the development of a complete organism from the parts of the body of the organism which are accidentally cut during an injury. This process is found in organism like-starfish, hydra, planaria etc.
Regeneration in Planaria:
Planaria have the ability to give rise to new individuals from their body parts. This process is called regeneration. If the body of Planaria is somehow cut or broken up into many pieces, each piece grows into a complete organism. Regeneration can take place from any part of the Planaria.