Alexander Khamalov, a physicist at the University of Coimbra in Portugal, discovered the effect by accident. For a laugh, he placed an apple in a device for measuring fluorescence – light emited by an object when struck by light of another wavelength. To his surprise, the pungent gases given off by the apple produced light when excited by the machine’s laser. How they might do this is not khown. “In theory volatile organic gases should not fluoresce. So I was very surprised,” he says. (10)