The Planck satellite has produced the first whole sky map of polarization|at sub-mm and mm wavelengths. This is an immense step forward from|earlier polarization observations of Galactic dust. The data is revealing a new|sky we have started to explore. For the first time, we have the data needed to characterize the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence, in the diffuse interstellar medium and molecular clouds. Our analysis of the data also involves the characterization of the polarization properties of dust. I will introduce the science questions we are investigating and review our published results. I will connect what we are learning on the astrophysics of dust polarization to the structure of the dusty polarized screen to CMB polarization at high Galactic latitudes.