Conceived the nuclear chain reaction in 1933, and patented several important inventions, such as the electron microscope, the linear accelerator, the cyclotron, and the idea of a nuclear fission reactor.

After the Nazi rise to power, Szilard fled Germany for Britain and assisted refugee scholars in finding new jobs. Forseeing another European war, he moved to the US to work on creating a nuclear chain reaction. In 1939, he wrote the letter for Albert Einstein's signature that resulted in the Manhattan Project.