Antimatter
Albert Einstein found a formula that can show how much energy a certain amount of something has, whether it is matter or antimatter. This formula is , and is one of the most well known equations. In simple terms, if you take the mass of something and then multiply it by the speed of light, and then multiply it by the speed of light again, you will get how much pure energy a given piece of something has. Since the speed of light is such a big number, this means that even a small amount of matter can have a lot of energy (it has been projected to be 4 times more effective per mass than nuclear fission).