Albert Einstein (March 14, 1879 - April 18, 1955) was a German-born American theoretical physicist who is widely regarded as the greatest scientist of the 20th century.
He proposed the theory of relativity  and also made major contributions to the development of quantum mechanics, statistical mechanics, and cosmology.
He was awarded the 1921 Nobel Prize for Physics for his explanation of the photoelectric effect and "for his services to Theoretical Physics". ( http://www.mlahanas.de/Physics/Bios/AlbertEinstein.html )

A Look at Young Einstein
The Middle Ages
Theory of Relativity
Bibliography