Different amyloid beta (Aβ) 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 Aβ aggregation states, which result from the formation of low molecular weight oligomers, high molecular weight oligomers, protofibrils, and fibrils.