The trio of researchers has published their work in the Proceedings of the National Academy of Sciences (PNAS).
They recreated viral videos that showed YouTubers cutting a grape in half, leaving only a sliver of skin connecting the two halves, and then microwaving the fruit.
Within seconds of being microwaves, the two halves of a grape would suddenly explode into a fireball, despite not containing any obviously flammable material.
There were multiple hypotheses suggested at the time to explain the explosion, including that the grapes formed a kind of antenna directing microwaves across the skin bridge. However, the real reason is even simpler.
As microwaves enter the grapes, hot spots form at the points where the fruit objects are closest to each other.
As the microwaves continue to heat the grapes, the hot spots get even hotter and the electrolytes surrounding them become supercharged, forming plasma - an ionized or electrically charged gas - which bursts in a fireball.
This method of producing plasma isn't unique to grapes, and the researchers were able to replicate it in similar-sized fruit as well as water-filled balls.
They also found that a physical connection between the objects was unnecessary as the bond was driven by an electric charge, they just needed to be close enough together.