data 5dThe lifetime of 5D memory is 10^20 years at room temperature, indicating unprecedented stability among all techniques. Besides the benefits of multiplexing, 5D optical data based on nanogratings can be also erased5D optical storage readout. (a) Birefringence measurement of the data record in three separate layers. (b) Enlarged 5×5 dots array. Pseudo colour indicated the orientation of slow axis.