There have been occasions when the publication of a particular book has had a singular impact on the conceptual world of the chemist. Sometimes the publication occurs near the beginning of a major change in discourse, and sometimes more near the end. Jean Perrin published Les Atomes in 1913 as the culmination of a century-long controversy over the size and physical reality of atoms and molecules. After its publication almost all chemists and physicists agreed that atoms and molecules of the (...) size we currently understand to be appropriate are real physical objects. The story of the background, development, publication, content and response to Les Atomes forms the text of this paper. The content of Les Atomes is also the basis for extended reflection on the philosophical significance of the work of Jean Perrin. (shrink)