Max Planck was often called a revolutionary, although he was against it. In 1900, the scientist put forward the idea that energy is not emitted continuously, but in the form of portions, or quanta. An echo of this hypothesis, which upended existing ideas, was the development of quantum mechanics - a discipline that, together with the theory of relativity, underlies the modern view of the Universe. Quantum mechanics examines the microscopic world, and some of its postulates are so surprising that Planck himself admitted more than once that he could not keep up with the consequences of his discoveries. A teacher of teachers, he stood at the helm of German science for decades, managing to maintain a spark of intelligence during the dark period of Nazism.