This book provides an insight into the depth and rich possibilities of the sophisticated technology of mass spectrometry that has brought Nobel Prizes to seven successive generations of scientists. The book first introduces the principles of mass spectrometry and how it will continue to change our lives. It is, so to speak, a reportage on the front lines. Then, this cutting-edge technology is briefly explained. By this, the author introduces both science and humanities majors alike to consider "what new worlds have been opened up by the power of measuring molecules," and how science is being applied to our society. This book covers the 100-year history of mass spectrometry and trends in a wide range of fields such as the latest medical diagnostics, environmental science, personal safety, and food safety. It also serves as an excellent introduction to the study of mass spectrometry. It provides easy access for those who intend to work or conduct research using mass spectrometry techniques, such as science and engineering technicians, graduate students, physicians, pharmacists, and clinical technologists. For those already engaged in the field, it will be helpful in learning about the latest trends and predicting future developments.