Title: Unravelling the physics of particle acceleration and magnetic fields in galaxy clusters Abstract: Most of the baryonic Universe is made up of poorly understood magnetised plasma, residing in the large-scale cosmic web. At the nodes of the cosmic web, galaxy clusters form the Universe’s largest gravitationally-bound building blocks. There, the intracluster medium (ICM) emits strong thermal X-ray and non-thermal diffuse radio emission. The emission is fueled by the turbulent injection of energy due to cluster mergers which heat the ICM, amplify magnetic fields and accelerate particles to ultra-relativistic energies. Although much process has been made in recent decades, many properties of the magnetic fields in clusters and the particle acceleration process are still unknown. In this talk, I will show how polarimetry and low-frequency radio observations advance our knowledge of cosmic plasmas in clusters. I will present deep and ultra-low frequency LOFAR observations which allow us to study rarely explored clusters, and results from a VLA survey of massive clusters where we have detected the imprint of the cluster magnetic fields through the statistical depolarisation of radio sources.