The book describes the branch of astronomy in which processes in the universe are investigated with experimental methods employed in particle-physics experiments. After a historical introduction the basics of elementary particles, Astroparticle Physics describes their interactions and the relevant detection techniques. The main body of this treatment concerns cosmic rays, while modern aspects of astroparticle physics are described in a chapter on cosmology. The book provides an orientation in the field of astroparticle physics that many beginners might seek and appreciate. The underlying physics fundamentals are presented with little mathematics, and the results are illustrated by many diagrams. The reader has a chance to enter this field of astronomy with a book that closes the gap between expert and popular level.