The accumulation of amyloid-beta (A beta) aggregates is found in the brains of Alzheimer's disease patients. Thus, numerous efforts have been made to develop chemical reagents capable of targeting A beta peptides and controlling their aggregation. In particular, tunable coordination and photophysical properties of transition metal com-plexes, with variable oxidation and spin states on the metal centers, can be utilized to probe A beta aggregates and alter their aggregation profiles. In this review, we illustrate some rational strategies for designing photo-activatable metal complexes as chemical sensors for A beta peptides or modulators against their aggregation path-ways, with some examples.