E=mc². Albert Einstein's most famous equation explains things of sheer wonder and beauty – why the sun shines and how the Big Bang created the universe. But it also underpins the most destructive force ever unleashed on the planet – the nuclear bomb. Learn how Albert Einstein's great discovery went from being a mere set of symbols in a notebook to a weapon of mass destruction. It was a development so appalling to Einstein, that he would describe his involvement in the bomb as "his biggest blunder." Meet Leo Szilard, friend, colleague and the man who persuaded Einstein to use his influence to encourage construction of the bomb. It was Szilard who first came up with the concept of a chain reaction – vital to turning the power of E=mc² into a bomb – and who persuaded Einstein to write the fateful letter to President Roosevelt that would play a key role in the decision to build the bomb. But while both men were initially lauded for their contribution to science, they would in later years devote themselves to disarmament, global peace and the dismantling of the very bombs they helped create.