The properties of soft-matter thin films (e.g. liquid films, polymer coatings, Langmuir-Blodgett multilayers) nowadays play an important role in materials science.They are also very exciting with respect to fundamental questions: When liquids and polymers form thin films, they may be considered as trapped in a quasi-two-dimensional geometry. This confined geometry is expected to alter the properties and structures of these materials considerably. This volume is dedicated to the scattering of x-rays by soft-matter interfaces. X-ray scattering under grazing angles is the only tool for investigating these materials on atomic and mesoscopic length scales. A review of the field is presented with many examples.