A two-photon 3D optical storage system based on a photochromic diarylethene (1,2-bis(2-methylbenzo[b]thiophen-3-yl)hexafluorocyclopentene) and a highly efficient two-photon absorbing fluorescent dye (2,7-bis[4-(9,9-didecylfluoren-2-yl)vinyl]phenylbenzothiazole) is demonstrated. The figure shows two-photon fluorescent readout of data recorded by single-photon excitation. The system is suitable for recording data in thick storage media and providing a non-destructive readout method.