Implanted electronics could provide a clearer picture of what's going on inside the body to help monitor chronic diseases or progress after surgery, but biocompatibility issues restrict their use. Many materials commonly used in electronics cause immune reactions when implanted. And in most cases today's implantable devices must be surgically replaced or removed at some point, so it's only worth using an implant for critical devices such as pacemakers. Silk, however, is biodegradable and soft; it carries light like optical glass; and while it can't be made into a transistor or an electrical wire, it can serve as a mechanical support for arrays of electrically active devices, allowing them to sit right on top of biological tissues without causing irritation. Depending on how it's processed, silk can be made to break down inside the body almost instantly or to persist for years. And it can be used to store delicate molecules like enzymes for a long time.You've got to love innovation in medicine.