Animal regeneration is the ability of certain animals to regrow lost body parts. This remarkable process is seen in species like axolotls, starfish, and planarians. When these animals lose a limb or tail, specialized cells called stem cells activate and begin to divide, forming new tissues to replace what was lost. The regeneration process varies among species. For example, axolotls can regenerate entire limbs, while starfish can regrow lost arms and even regenerate a whole new body from a single arm. Scientists study these processes to understand the underlying mechanisms, which could have implications for medical advancements in humans.