Photoactivatable fluorophores are powerful imaging probes for tracking molecular and cellular dynamics with high spatiotemporal resolution. We have designed and synthesized a new caged FREr dye, CCC-1, comprising a caged cournarin and a water soluble xanthene dye. CCC-1 can be efficiently photolyzed by ultraviolet light. Its photolyzed product, CC-1, emits strong green fluorescence with a FREr efficiency of 95% when excited near 410 nm. The uncaging cross section of CCC-1 is about 6000 M-1cm-1 at 365 nm, more than a hundred times higher than caged fluoresceins developed previously. The probe is also blocompatible and has built-in functionalities for bioconjugation.