This proposal combines optical spectroscopy with neutron scattering using novel labelling strategies to investigate ?amyloid? protein fibrils. Variations in packing and in the dynamics of elongation and breakage underpin phenomena ranging from non-genetic heredity in yeast, to diseases such as Alzheimer?s, BSE and CJD. Most solution methods to monitor growth dynamics only give information on the overall % of material transformed from non-fibrillar to fibrillar forms. They cannot determine length distribution or linear growth rates, but instead convolute the two; in other words, they cannot distinguish a few long fibrils each growing quickly, from many short fibrils each growing more slowly. We will determine both fibril lengths and linear growth rates using SANS and insitu optical spectroscopy.