The aggregation of the Amyloid beta (Abeta) peptide is implicated in the progression of Alzheimer's disease, the treatment of which is a major current global healthcare challenge. It has recently been reported that oligomeric states, formed before aggregation into fibrils, may be the toxic disease-causing species. Contrast variation SANS provides a unique in situ method to elucidate the structures formed at intermediate stages of fibrillization. We will perform SANS experiments on Abeta(1-40) and Abeta (1-42) to investigate the structure of intermediate structures including oligomeric species. For the first time, we will perform SANS on defined oligomeric states (prepared using in vitro methods from amyloid seeds, or using expressed species) as widely studied in the literature using ex situ methods such as TEM.