When we have found how the nucleus of atoms is built up we shall have found the greatest secret of all — except life. We shall have found the basis of everything — of the earth we walk on, of the air we breathe, of the sunshine, of our physical body itself, of everything in the world, however great or however small — except life.

As quoted in The Wit and Wisdom of the 20th Century : A Dictionary of Quotations (1987) by Frank S. Pepper, p. 226