According to Einstein’s famous equation E=mc^2, anything with mass has a huge amount of energy. Well, there are basically three ways to generate energy: chemical reactions, nuclear reactions, and gravitational reactions (like matter falling into black holes). But unlike chemical reactions and nuclear reactions, gravitational reactions are the most efficient. In gravitational reactions, the energy comes from what stuffs does while falling towards the black holes before reaching the event horizon (the point of no return). Find out how the matter falling into black holes contribute to making gravitational reactions as the most efficient form of converting mass into energy in the video.