Different amyloid beta (A beta) aggregates can be discriminated by a combinatorial fluorescent molecular sensor. The unique optical fingerprints generated by the unimolecular analytical device provide a simple means to differentiate among aggregates generated from different alloforms or through distinct pathways. The sensor has also been used to track dynamic changes that occur in A beta aggregation states, which result from the formation of low molecular weight oligomers, high molecular weight oligomers, protofibrils, and fibrils.