This accessible introduction 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 emphasis is cosmic rays, while modern aspects of astroparticle physics also treated in a cosmological content. It provides an orientation in the field of astroparticle physics that many beginners might seek and appreciate because 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.