With a new class of imaging polarimeters it is now possible to
eliminate the previous main limiting factors of seeing and gain-table noise in the polarization images to allow spectro-polarimetry with a precision of 5 × 10-6. This has opened the door to a previously unexplored world of polarization phenomena with promising diagnostic possibilities not only for the Sun but also for night-time astronomy. While illustrating examples of what has been achieved,
we present an overview of the new opportunities and quantify the limitations imposed by the photon flux.