The aqueous supernatants resulting from ultracentrifugation of brain samples from patients with Alzheimer’s disease (AD) contain aggregates so far described as soluble oligomers of amyloid-β protein (Aβ), which are responsible for the neurotoxicity underlying AD and thus considered targets to watch in this devastating condition. Now, a group of scientists from Harvard Medical School have determined that these aggregates are in fact insoluble diffusible fibrils with the same atomic structure as plaque fibrils.