Isaac Asimov was a renowned science fiction author, best known for his Foundation series. He was born in Russia in 1920 and moved to the United States in 1923. Asimov wrote or edited more than 500 books and an estimated 90, 000 letters and postcards. He is considered one of the most prolific writers of all time. Asimov's works have been published in nine out of ten major categories of the Dewey Decimal System. He is widely regarded as one of the greatest science fiction authors of all time.