Polarimetry is established as the third eye of humankind into the Universe, complementing photometry and spectroscopy. Dust and magnetic fields are ubiquitous the Universe and widely thought to play crucial roles in many astrophysical processes, from star formation and stellar feedback to planet formation, molecule formation, and life. Polarization of light induced by alignment of dust grains with magnetic fields is a leading tool for illuminating the dusty and magnetized universe from the UV-optical-NIR to far-IR and (sub-)mm wavelengths. The most powerful observatories (ALMA, NOEMA, IRAM/Nika2-Pol, SOFIA/HAWC+, JCMT/Pol2, APEX/A-mKID, TolTec, BLASTPOL) are providing a vast amount of polarization data, which promise to shed light on the fundamental dust physics (e.g., grain alignment and rotational disruption) as well as the key role of dust and magnetic fields in many astrophysical processes. In this talk, I will comprehensively review the current state-of-the-art of our theoretical frameworks, computational tools, and observational constraints of dust physics and magnetic field properties using multi-wavelength polarization data. I will then introduce a new technique for probing 3D magnetic fields using dust polarization and our grain alignment theory.