High sensitivity polarimetry

Over the last decade spectro-polarimetry evolved to ever higher sensitivity levels. New techniques and instruments allow us to address weak polarization signals, which are caused by scattering in the solar atmosphere. In this paper a review on the development of spectro-polarimetric investigations of scattering physics and its coupling to the solar magnetic field will be given. Starting from a technical point of view it will be demonstrated how our understanding of scattering phenomena and their role in solar physics in general has reached its current state. An outlook on future spectro-polarimetry with new large solar telescopes concludes this review.