Extragalactic jets shine across the entire electromagnetic spectrum, emitting radiation from radio waves up to very high-energy gamma rays. In the past decades, astrophysicists have been able to grasp several aspects of the functioning of these structures, thought to be launched by rotating magnetic fields close to the horizon of supermassive black holes. One of the most basic questions about jets is the one related to the nature of the radiating particles and the mechanisms at the base of the emission that we observe…