Organic compounds as carriers of the diffuse interstellar bands

The diffuse interstellar bands appear as absorption features in spectra of reddened stars and lie mostly in the visible region of the spectrum. The first examples were recorded photographically nearly one hundred years ago and despite a huge amount of observational, theoretical and laboratory effort the spectra remain unassigned. Most researchers believe that organic material is responsible for the absorptions, the most popular form being polycyclic aromatic (hydro)carbon (PAH) structures. This article reviews briefly the main characteristics of the spectrum, describes some current research and outlines some lines of inquiry.