We are accustomed to implants designed for permanence — titanium devices intended to last a lifetime, and polymers with variable long-term behavior. However, some materials are designed to function temporarily and then safely degrade once their role is complete. Magnesium is one such material. This lecture examines how biodegradable metallic implants can be engineered to degrade in a controlled manner without harming the body. The work is driven by a megagrant-funded research team: a lab built from the ground up, successive experimental series, animal models from rodents to minipigs, and patients who already receive such implants.