The mystery of the diffuse interstellar bands has been variously a curiosity, a co nundrum, and a nuisance for astronomers in the seven decades since the featur

The existence of subparsec structure in the cold diffuse interstellar medium has been the subject of some debate. After a review of the literature, we will pres

The interstellar medium (ISM) is organized in different phases with distinctive temperatures, densities, and ionization. The complex interplay between the diffe