SignificanceAlzheimer’s disease is a devastating neurodegenerative disease and the most common cause of dementia. It involves the self-assembly of the amyloidβpeptide into fibrillar aggregates through an autocatalytic amplification mechanism—secondary nucleation. This study investigates the mechanism of surface-catalyzed secondary nucleation and asks whether it has a templating role in which nucleating species take up the structure of the parent fibril. This is important in understanding the formation of oligomers, which are considered to be the neurotoxic species during the disease. The results provide a high-resolution view of secondary nucleation and show the steps of attachment, growth along the fibrils and finally detachment and appearance of new fibrils.