Typical defibrillators use electric pulses that can damage heart tissue — light would be a safer (not to mention gentler) way of tackling a patient's irregular heartbeat. The science is based around optogenetics, where light-sensitive proteins are attached to living tissues. When light hits these proteins, they can modify the electrical activity inside your cells.

A team from Germany's University of Bonn tested mouse hearts whose cells had been genetically engineered to produce proteins that could be triggered by light. One-second light pulses were all that was needed to restore a regular heartbeat.

Scientists at John Hopkins then designed a human heart sim, noting that the blue light used by the German team on the smaller mouse hearts wasn't strong enough for human heart tissue. Red light, with a longer wavelength, was more effective -- at least according to their computer simulation. Optical defibrillators aren't coming any time soon; it will still take around five to ten years before the technology is ready for human patients.