The process of getting back a full organism from its body parts called regeneration. The simple animals like hydra and planaria show regeneration.
Planaria is a type of flatworm. It has the amazing capacity to regenerate its lost body part. When the flatworm is cut horizontally, separating the head from the tail, the tail will regenerate the lost head and the head will regenerate the lost tail. This process is known as regeneration. The diagram illustrating the process of regeneration in Planaria is given below.
Regeneration is one of the methods of asexual reproduction, which can be observed in Hydra also.