Grapes have an ion-rich liquid that is their juice. This juice conducts electricity. All you have to do is to cut this seedless grape into two halves. But keep in mind that you don’t cut the piece completely.
The grape should remain connected to one another with a small piece of skin.
When you place it in the oven the ions move back and forward very quickly between the two halves. This movement heats the skin bridge which erupts into flames. At this point the traveling electrons arc through the flame and across the gap, ionizing the air to plasma and further creating the bright flashes.
Via: hackedgadgets
