This is a short booklet on science fact commissioned by the U. S. Energy Research and Development Administration (Office of Public Affairs). It tells the story of the origins of nuclear physics in terms understandable to an audience with minimal technical background. What were the steps through history - the discoveries that built upon one another - from alchemy to chemistry, physics, astronomy, mathematics, and quantum mechanics, that led to our understanding and harnessing nuclear energy? Asimov was a great writer of both science fact and fiction who wrote or edited more than 500 books, published in 9 of the 10 major categories of the Dewey Decimal Classification.