Novel instruments for high-precision imaging polarimetry have opened new possibilities, not only for diagnostics of magnetic fields, but also for exploring effects in radiative scattering, atomic physics, spectral line formation and radiative transfer. The observational advances have stimulated various theoretical developments, for instance in vector radiative transfer and techniques for inverting polarized line profiles. The present volume gives a comprehensive and up-to-date account of this rapidly evolving and interdisciplinary field of science. It is based on the oral presentations given...