Albert Einstein did not really start talking until he was about 3 years old, which concerned his parents. He was born into a middle-class German family. When Einstein was only 15 years old, he dropped out of high school, following his family to Italy. In 1905, Albert wrote four "fundamental papers," in the fourth one, he showed that mass and energy are two parts of the same thing, thus producing E=mc^2. In 1909, he became a professor at the University of Zurich. In 1915, after many years of thought put into it, Albert finally finished his general theory of relativity. In 1924, Einstein contributed to the new quantum theory. In 1939, Einstein had signed a letter that led President Roosevelt know about the possibility of German development of nuclear bombs. Albert Einstein died in the year 1955.