Researchers have designed a graphene-based tattoo that can be directly laminated onto the skin with water, similar to a temporary tattoo. But instead of featuring artistic or colorful designs, the new tattoo is nearly transparent. Its main attraction is that graphene’s unique electronic properties enable the tattoo to function as a wearable electronic device, with potential applications including biometric uses (such as measuring the electrical activity of the heart, brain, and muscles), as well as human-machine interactions.