Ruthenium-bipyridine-triphenylphosphine caged glutamate that can be excited by visible wavelengths and releases glutamate after one- or two-photon excitation. Has high quantum efficiency and can be used at low concentrations, partly avoiding blockade of GABAergic transmission seen with other caged glutamate compounds. Display high spatial resolution and generates excitatory responses in individual dendritic spines with physiological kinetics.