Well humans are the only animals that are not equiped with the ability to regenerate as other animals do. But we have come across an ability to take and scrape off pigs skin a substance and bio engineers use a powder to help it grow, than they apply it to human muscles to actually regrow muscles.
Yeah true, this guy had his legs blown up in war. It was bad! Lots of muscle was missing and they applied this stuff and regrew his muscles. pretty cool!