Biophoton emission now belongs to a topical field of modern science: It concerns a weak light emision from biological systems. Such molecular events are clearly compatible with collective phenomena as shown by recent developments in the life sciences such as the chaos theory. This book is concerned with the "optical window" of biological interactions and in view of their correlations to many biological functions they provide a powerful, non-invasive tool of analysing biological systems. Topics include food science, pollution, efficacy of drugs including the treatment of cancer and immune diseases, and communication phenomena such as consciousness.The collection of articles in this book covers the historical background, the physics of biophoton emission, those biological phenomena which show evidence of a "holistic" character, and finally discusses applications and biological evolution. This volume serves to bring researchers up-to-date on the subject and draws attention to the many exciting findings that are widely scattered in the scientific literature.