This book deals with the astrophysics and spectroscopy of the interstellar molecules. In the introduction, overview and history of interstellar observations are described in order to help understanding how the modern astrophysics and molecular spectroscopy have been developed interactively. The recent progress in the study of this field is briefly summarized. Furthermore, the basic knowledge of molecular spectroscopy, which is essential to correctly comprehend the astrophysical observations, is presented in a compact form.

The book is an up-to-date, concise presentation of the development of submillimeter-wave and far-infrared astrophysics. The topics range from the large-scale atomic and molecular distribution in the Galaxy and in external galaxies to the frontal properties of molecular clouds and the details of the star-formation process. A chapter on the most recent technical advances in the field illustrates the intimate connection and interplay between scientific advancement and technological capability. The book not only summarizes the advances in the field but also presents important background information, addressing experts and graduate students alike.