Multi-wavelength observations over the last decades proved the existence of observationally very diverse manifestations of isolated NSs (INSs) and led to the separation of INSs into distinct classes. Most of the ~2,300 known INSs are radio pulsars with periods P < 8 s and magnetic field B ~ 10 12 G, but there are objects with much greater potential for understanding the INSs diversity. This includes: Magnetars, X-ray Dim INSs (XDINSs), high-B rotation powered pulsars, Rotating radio transients (RraTs) , and Central Compact Objects (CCOs). In this talk I will focus on the observational properties of XDINSs and magnetars. I will present a summary of the phenomenology with focus on the X-ray properties. I will then review future perspectives for X-ray timing and Polarimetry.