Leo Szilard was born in Budapest, Hungary, on February 11, 1898. He left Germany in 1933 because of anti-Jewish laws. With the news that German scientists discovered nuclear fission, Szilard immediately set up a series of experiments, in collaboration with Enrico Fermi, to see if the theory was correct.

Enrico Fermi was born in Rome, Italy on 29th September, 1901. Won the Nobel Prize in 1938 and immediately emigrated to America, primarily to escape Mussolini's fascist dictatorship. He lead the team that created the first self-sustaining nuclear chain reaction.

Stanislaw Ulam was born on April 3, 1909 in Lvov, Poland. He fled Poland in 1939 and found a position at Princeton. Invited by Hans Bethe, he arrived at Los Alamos in 1943. He developed the ‘Monte-Carlo' method, which greatly aided in creating an atomic bomb.

Albert Einstein born in Württemberg, Germany, on March 14, 1879. In 1933 he renounced his citizenship for political reasons and emigrated to America to take the position of Professor of Theoretical Physics at Princeton. He became a United States citizen in 1940.

Eugene Wigner born in Budapest, Hungary, on November 17, 1902, naturalized a citizen of the United States on January 8, 1937. He worked with Fermi at the Metallurgical Laboratory, from 1942 to 1945 determining whether a fission-induced chain reaction was possible.

Edward Teller born in Budapest, Hungary in 1908. Immigrated to US 1935 and became a citizen in 1941. Considered, "the father of the hydrogen bomb", he credits Werner Heisenberg with launching his career in physics.

Hans Bethe born in Strasbourg, Germany on July 2 1906. He lost his university position because his mother was Jewish, then emigrated to England in October 1933. He moved to Cornell University in the US in 1935. As the director of the theoretical division for the Manhattan Project, his group calculated how much fuel was needed for the bombs.

Emilio Segré was born in Tivoli, Rome, on February 1, 1905. Emigrated to the US in 1938 and lead the Radioactivity Group at Los Alamos. Their discovery of spontaneous fission of plutonium led to the reorganization of the Laboratory in the summer of 1944.

John von Neumann was born December 28, 1903 in Budapest, Hungary. He moved to Princeton University in 1930 and in 1943 von Neumann began working on the Manhattan Project, where he tackled the immense calculations required for construction of an atomic bomb.