One- and two-electron ions traditionally serve as an important testing ground for fundamental atomic structure theories and for investigation of QED, relativistic and correlation effects. In the domain of high nuclear charges, new opportunities open up for precise testing and consolidating of the present understanding of the atomic structure, in the regime of extreme electromagnetic fields. In this article, the current progress in experimental investigations of the heaviest H- and He-like systems at GSI Darmstadt is presented. In addition, the planned future experimental studies and developments devoted in particular to high-resolution spectroscopy of excited states in heavy He-like ions as welt as of the is state in hydrogen-like systems, are reviewed.