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Being fast rotating objects, Isolated Neutron Stars (INSs) are natural targets for high-time resolution observations across the whole electromagnetic spectrum. With the number of objects detected at optical (plus ultraviolet and infrared) wavelengths now increased to 24, high-time resolution observations of INSs at these wavelengths are becoming more and more important. While classical rotation-powered radio pulsars, like the Crab and Vela pulsars, have been the first INSs studied at high-time resolution in the optical domain, observations performed in the last two decades have unveiled potential targets in other types of INSs which are not rotation powered, although their periodic variability is still related to the neutron star rotation. In this paper I review the current status of high-time resolution observations of INSs in the optical domain for different classes of objects: rotation-powered pulsars, magnetars, thermally emitting neutron stars, and rapid radio transients, I describe their timing properties, and I outline the scientific potentials of their optical timing studies.

So far, 24 Isolated neutron stars (INSs) of different types have been identified at optical wavelengths, from the classical radio pulsars to more peculiar objects, like the magnetars. Most identifications have been obtained in the last 20 years thanks to the deployment of modern technology telescopes, above all the HST, but also the NTT and, later, the 8m-class telescopes like the VLT. The larger identification rate has increased the impact factor of optical observations in the multi-wavelength approach to INS astronomy, opening interesting possibilities for studies not yet possible at other wavelengths. With the HST on the way to its retirement, 8m class telescopes will have the task of bridging neutron star optical astronomy into a new era, characterised by the advent of the generation of extremely large telescopes (ELTs), like the European ELT (E-ELT). This will mark a major step forward in the field, enabling one to identify many more INSs, many of which from follow-ups of observations performed with future radio and X-ray megastruscture facilities like SKA and IXO. Moreover, the E-ELT will make it possible to carry out observations, like timing, spectroscopy, and polarimetry, which still represent a challenge for 8m-class telescopes and are, in many respects, crucial for studies on the structure and composition of the neutron star interior and of its magnetosphere. In this contribution, I briefly summarise the current status of INS optical observations, describe the main science goals for the E-ELT, and their impact on neutron star physics.

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