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Ahmed Zewail was born in Egypt and later became a naturalized American citizen. He is a Nobel Prize-winning chemist who is best known for his work on femtochemistry, the study of chemical reactions on a timescale of femtoseconds (10-15 seconds). Zewail's work has helped to revolutionize our understanding of the chemical bonds that hold atoms together, and has led to the development of new technologies for studying chemical reactions.