Organic circuitry that, as the name suggests, is tattooed onto individuals. When an individual undergoes rejuvenation, the OCtattoos are removed from the body and new ones are needed. These are susceptible to antibody attack but generally last for decades. In 2015 first steps towards real-world OCtattoos were reported by researchers at the University of California, San Diego (UCSD), who developed sensor inks capable of monitoring blood sugar levels and detecting other problems such as toxic pollutants and nerve agents.