A trio of researchers with McMaster, Concordia and Trent Universities has solved the mystery of why pairs of grapes ignite into fireballs when cooked together in a microwave oven. In their paper published in Proceedings of the National Academy of Sciences, Hamza Khattak, Pablo Bianucci and Aaron Slepkov claim that the fireball is not the result of heat from the outside of the grapes making its way in, but instead comes about due to hotspots that form in both grapes.