Thanks to the radio data provided by new instruments, such as LOFAR, we expect to fully understand non-thermal phenomena in clusters. However, recent observations revealed details on the non-thermal component that cannot be explained by the previously thought mechanisms. There are several open questions that this field needs to tackle to bring our understanding to a deeper level. The main goal of this workshop is to bring together the community working on non-thermal emission in clusters from different angles – theory, simulations and observations – in order to unveil the origin of this emission and its connection with the structure formation process. We plan for a workshop with about 60 participants, with several invited talks, some slots for contributed talks, and guided discussion sessions well prepared in advance by the SOC in collaboration with the invited experts to tackle relevant questions.