As in all nonlinear optics, control over the spatial phase of the fundamental light fields allows extensive influence on the well-established effect of High-Har monic Generation (HHG). This results in the realisation of coherent extreme ultraviolet (XUV) light with unique properties. Christian Kern shows and discusses in his thesis two schemes where phase shaping of ultrashort laser pulses is appli ed on scales below their fundamental wavelength. He shows the limitations of how nanoplasmonic objects can be administered for strong field physics. Furthermore, a novel approach of producing XUV light carrying orbital angular momentum via HHG is demonstrated and experimentally verified.