In further tests,Khamalov and his colleague Hugh Burrows discovered that it's not just the fluoresce. The apple's also seems to have something to do with it. "The membrane is clearly important," says Burrows. "When the gas molecules come up against the porous membrane of the skin,only the most energetic make it through," the researchers speculate. They believe these molecules are in a most excited of vibration than usual. When the laser light hits the molecules, they drop into a lower vibration state, releasing energy in the from of light. "Initially, I was very sceptical," says Burrows. "But the result seems genuine.