This is a short booklet on science fact commissioned by the U. S. Energy Research and Development Administration . 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.