Abstract: Since the discovery of the presence of fibrillary forms of α-synuclein (α-syn) in Lewy bodies (LB) and Lewy neurites in the brain of patients affected by Parkinson’s disease (PD) and dementia with LB, great effort has been dedicated to study the features of α-syn fibrillation. In parallel, the pathological relevance of the different toxic forms of α-syn has been also matter of investigation. In the last twenty years, scientists have been able to single out that α-syn fibrillation initiates pathological mechanisms that by contributing to or triggering neurodegeneration/neuroinflammation, may lead to PD pathogenesis. This notwithstanding, we still ignore the reasons why α-syn shifts from its natively unfolded conformation to toxic oligomeric and fibrillary forms. The chameleonic nature of monomeric α-syn, and the extremely polymorphic characteristics of aggregated strains, renders it difficult to picture the real nature of α-syn fibrils, their exact composition and formation dynamics. Recently, sophisticated biophysical methods and microscopy techniques have been exploited to study α-syn fibrillation. Here, we provide an overview of the most relevant advancement in our understanding of α-syn fibrils formation and conformation. Nonetheless, numerous techniques and patient- derived experimental models still need to be optimized to actively disclose causes and characteristics of α-syn fibrillation in disease-specific cellular milieux.