In recent years, the microanalytical study of presolar materials in meteorites - including circumstellar and supernova grains - has provided a rich new source of information on nucleosynthesis, grain formation in stellar outflows and conditions in the solar nebula that permitted the preservation of these grains. At the same time, refinements in astronomical observations of interstellar and circumstellar dust, and the modelling of nucleosynthesis in stellar interiors and of the physical conditions in stellar ejecta have led to more realistic appraisals of the processes responsible for the composition, generation, and alteration of solid matter in the galaxy. This book contains contributions from a wide variety of scientists discussing new experimental, theoretical, and observational constraints on the nature of interstellar and circumstellar solids. It sets out to provide different points of view, necessary for unlocking the information preserved in these unique and rare materials, and is intended for scientists and graduate students in the fields of cosmochemistry, astrophysics, and astronomy.