This is a book about plant chemistry written by a herbalist with no claims of being a chemist. Having a driving ambition to understand the nature of herbal medicines—in particular what makes them work—I delved head first into the previously alien world of atoms, molecules and bonds. Having learned enough to be engaged to teach the topic to budding herbalists and naturopaths, I set about formalising the teaching notes—the result is the original (1996) edition of this text.