The work performed within the DFG Research Group centers about the electronic, magnetic and elastic properties of highly correlated transition metal chalcogenides. In particular, we concentrate on oxides and sulfides of the early transition metals like vanadium and chromium. Some of these compounds display a metal-insulator transition as a function of temperature or external pressure as well as exciting magnetic properties. In addition, doping e.g. with sodium or strontium allows for specific tailoring of the electronic and magnetic properties. Although all these phenomena open lay ground for very promising -- industrial -- applications, our present understanding of the driving force for the metal-insulator transition is still limited. This background marked the starting point of our activities: In close collaboration of experimentalists and theoreticians we are investigating the role of electron-electron correlations as well as of electron-lattice interaction.