Isaac Asimov (January 2, 1920 – April 6, 1992) was an American author and professor of biochemistry at Boston University, best known for his works of science fiction and for his popular science books. Asimov was one of the most prolific writers of all time, having written or edited more than 500 books and an estimated 90,000 letters and postcards. His works have been published in all ten major categories of the Dewey Decimal System (although his only work in the 100s—which covers philosophy and psychology—was a foreword for The Humanist Way).