Interstellar dust grains - an overview

During the last years our knowledge about the structure and chemical composition of cosmic dust grains has very much deepened mainly driven by the rapid progress in infrared observations, laboratory experiments, and a much better theoretical treatment of grain evolution and the microphysical interactions of solid particles with gas, radiation, and with each other. This contribution will review the progress in the understanding of cosmic grains especially concentrating on the different grain populations, the physical processes which they link together, and the morphological and chemical structure of the particles.