Benjamin Franklin, the inventor of the lightning rods, revealed in 1752 an experiment proving that the lightning has electric properties. He was the first one to realize that the sparks from an electrostatic machine behave as lightning bolts and, thus designed an experiment to prove that the bolt has electric properties. He used a kite to carry out this experiment, consisting of an iron wire (which was supposed to collect electricity) attached to the top of the kite and a rope.
Benjamin Franklin flew the kite during the storm. The sparks flew from the key tied to the bottom of the rope all the way to Franklin’s wrist. The experiment was painful but it proved the assumption: storm clouds contain electricity!