Weak gravitational lensing with SKA

I shall outline the basic principles and some observational aspects of weak gravitational lensing, and discuss several applications of this powerful tool in observational cosmology. It will be explained why the applications have been restricted to optical observations up to now, and why SKA is going to change this. I conclude with a few general remarks on a comparison between SKA and the NGST, both being facilities which will provide a tremendous step forward in radio and near-IR astronomy, respectively, into completely unknown territory.