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.