Cell-permeable fluorescent amyloid stain for in vitroamyloid beta staining in brain tissues. Used to detect amyloid fibrils and to study amyloid fibril structure and the mechanism by which they form. Stains insoluble senile Aβ plaques, confirms formation of β-sheet structure from mutant huntingtin exon-1 aggregates in vitro and may also be used to monitor polyglutamine amyloid formation of tNhtt-42Q aggregates in Huntington's diseases models in vitro.