In this proceeding we report the principles for a novel 3-D RET-based two-photon optical storage device based on a photochromic diarylethene (1,2-bis(2-methylbenzo[b]thiophen-3-yl) hexafluorocyclopentene (1) and a fluorene derivative (2,7-bis[4-(9,9-didecylfluoren-2-yl)vinyl] phenylbenzothiazole (2)), suitable for recording data in thick storage media. Data was recorded by linear (single-photon) and non-linear (two-photon) excitation of the closed form of diarylethene 1. The read-out mechanism is based on resonance energy transfer (RET) from fluorene derivative 2 to the closed form of diarylethene 1. Bright fluorescent data patterns were recorded onto the photosensitive film, providing excellent contrast and resolution. Two-photon characterization with a tunable mode-locked femtosecond Ti:sapphire laser gave evidence of the cycloreversion reaction from the closed to the open photoisomer by excitation at 800 nm. We demonstrated non-destructive readout of 3D data stored in multiple layers by using two-photon induced fluorescence modulation. Readout of the stored information can be done for >10,000 cycles without significantly compromising the stored data.