The study of the interstellar medium (ISM) is of great interest both for astrophysical processes in the local Universe, namely for star formation in the Galaxy, and for accurately probing the cosmic times, as the ISM is an unavoidable filter for primordial lights coming to us. The ISM is a mixture of cosmic rays, multi-phase gas, and dust particles, all coupled with magnetic fields. It is through their interactions that a complex, yet unclear, cycle leads diffuse/warm matter to condense into denser/colder regions, where new stars form partaking the Galactic evolution. For decades, one difficult challenge of observational Astrophysics has been the characterization of magnetic fields along this evolutionary sequence. Today, thanks to the technological breakthrough of new polarimetric facilities, such as the Planck satellite and the LOFAR radio telescope, we are now entering a new era to probe magnetic properties in the ISM.

In my talk I will give an overview of the recent results about the magnetized ISM and highlight the questions that these novel observations are raising. I will first guide you through the first all-sky maps of linear polarization at sub-millimeter wavelengths from Planck, which allowed us to trace the Galactic magnetic-field orientation weighted on the density structure of the ISM. Second, I will bridge these mesmerizing data with the capability of LOFAR to probe interstellar magnetic fields in the warm and ionized Milky Way. I will focus on two main aspects in the interpretation of the data: the role of magnetic fields in matter-structure formation from the diffuse ISM to the regions 
where star formation takes place; the impact of such ISM studies on high-precision cosmology stressing the synergy between the two fields.