Max Karl Ernst Ludwig Planck (1858-1947) was a German physicist who discovered quantum physics, initiating a revolution in natural science and philosophy. He is regarded as the founder of quantum theory. His 1900 paper describing black body radiation proposed that radiation must be emitted or received in energy packets (quanta), rather than continuously. Quantum theory was fully accepted after its successful prediction of the photoelectric effect (Einstein, 1905) and of the electronic structure of atoms (Bohr, 1913). Planck received the 1918 Nobel Prize for Physics for his work. The discovery of Planck's constant enabled him to define a new universal set of physical units (such as the Planck length and the Planck mass), all based on fundamental physical constants. When the Nazis seized power in 1933, Planck was 74. He witnessed many Jewish friends and colleagues expelled from their positions and humiliated, and hundreds of scientists emigrated from Germany. His youngest son, Erwin, was implicated in the attempt made on Hitler's life in the July 20th plot (1944). Erwin died at the hands of the Gestapo in 1945. Planck died in 1947 at the age of 89.