Biologists have “learned so much about how embryos grow that we have tentatively begun to tailor the process to our bidding,” says Juan Carlos Izpisúa Belmonte of the Salk Institute in the November Scientific American. As a result, he and other researchers have begun genetically modifying pig embryos with the hope they will eventually give rise to pigs that contain one or more human organs—the subject of his feature-length article “Human Organs from Animal Bodies.”

Belmonte's introduction to this particular field of research began with his study of the genes that allow some salamanders and other creatures to regrow severed limbs. In this video he describes a range of regenerative abilities and ponders whether humans might be able to tap such abilities for themselves.