Electronic tattoos are flexible electronic devices that can be stuck directly onto skin to monitor heart, brain, and muscle activity without irritation. They resemble small computer chips and are made of thin, wavy silicon structures containing circuits thinner than a human hair that conform to the skin's topography and stretch and shift with the skin. They can be worn for extended periods without causing the irritation that adhesive tapes and rigid electronics often produce. Electronic tattoos can deliver electrical impulses in living tissue to prevent epileptic seizures or monitor heart functions in real-time and detect muscle movement, heart activity, and brain waves to allow doctors to noninvasively diagnose and monitor conditions like heart arrhythmia or sleep disorders.