By implementing "The Chain Reaction," we aim to bridge the "mobility gap" for 30 young people, including marginalised youth, by transforming the bicycle into a tool for social and economic independence. Our primary objective is to move beyond recreational cycling to establish a "Living Lab" environment where participants gain high-level technical agency, mechanical skills, and the confidence to navigate complex urban infrastructures. From a youth work perspective, the project seeks to foster active citizenship by empowering participants to transition from passive transport users to "Mobility Ambassadors." We aim to provide these youth with recognized non-formal competences, such as technical problem-solving and spatial justice advocacy, that improve their employability and civic engagement. Ultimately, the project intends to trigger a sustainable "Chain Reaction," where participants return to their home communities in Bulgaria, Italy, and Spain to lead peer-to-peer workshops and advocate for inclusive, green urban transformation.