Our studies revolve around the small sizes of silver clusters. These molecular metals have discrete electronic states, localized optical transitions, and strong fluorescence. DNA strands serve two purposes: (1) Their nucleobases coordinate specific species, and specific sequences yield chromophores with spectra that span the visible and near-infrared spectral regions; (2) They direct cluster transformations via changes in their secondary structure. Our studies revolve around pairs of chromophores that interconvert via hybridization. These conjugate cluster-DNA chromophores are innovative because of two features – hybridization switches on fluorescence and two-color laser excitation enhances the overall cluster emission. Mass spectrometry and X-ray absorption spectroscopy establish the basis for the fluorescence switching. Changes in the stoichiometry, charge, and structure of pairs of dim/bright chromophores are investigated. Fluorescence correlation spectroscopy evaluates the basis for the two-color enhanced fluorescence. These two sets of studies will provide the foundation to develop a new class of optical sensors. These sensors will be used to detect low abundance microRNA sequences that are relevant for early cancer intervention.