We have developed scanning nonlinear dielectric microscopy (SNDM) for observation of ferroelectric polarization distributions range. We also have studied high-density ferroelectric data storage using this microscope. In this study, we selected a stoichiometric (SLT) and a congruent (CLT) lithium tantalate (LiTaO3) single crystal- thin plates, with 180° C-C domain only, as a specimen. At first, as basic investigation of domain engineering, we revealed the relationship between applied voltages to SLT sample and inverted domain sizes, and also clarified the inverted domain size as a function of voltage applying time. As a result, we succeeded to obtain nano-sized domain inverted dots. These very small nano-domain dots were quite stable with time. Finally, in the CLT single crystal thin plate, whitch is expected that higher-density strage is possible, we performed actual data storage with the density of 1.5 Tbit/inch2.