Tokamaks represent one of the most promising candidates to develop nuclear fusion on Earth. Modern tokamaks such as ITER, JET or WEST use high-Z elements like tungsten (W, Z=74) as plasma-facing components, to limit the retention of tritium that was observed with traditional carbon walls. Nevertheless, the presence of high-Z impurities in the plasma, due to wall erosion, brings important new challenges that need to be investigated to pave the way for efficient fusion reactors. The goal of this lecture is to present some key aspects and recent advances related to this topic, with a focus on X-ray tomography diagnostic methods to monitor the transport of high-Z impurities in tokamak plasmas.