"Since the discovery of two–dimensional and meta–stable graphene sheets, the recent years have witnessed a dramatic increase in the research dedicated to explore its physical properties. This can be attributed to the two following reasons. First, graphene allows one to address basic questions of quantum mechanics such as relativistic Dirac fermions or the Klein paradoxon in a simple condensed–matter experiment. Second, the nanometer size, the scalability and room–temperature ballistic transport properties make graphene a promising candidate for future nanoelectronic devices with high electronic mobilities and an ideal material for spintronics. In this proposal, the spectroscopic investigation of functionalized mono– and few–layered graphene (FLG) is suggested. The samples are already available as graphene layers grown by precipitation on SiC and by chemical vapour deposition on metal (111) surfaces and as graphite intercalation compounds (GICs), consisting of stacked layers of doped graphene sheets. Their electronic, vibronic and optical properties as a function of functionalization will be investigated by optical spectroscopies, photoemission and electron energy loss. We utilize a combined experimental and theoretical approach in order to gain a deep understanding of graphene physics. Particular emphasis will be paid to electronic correlation effects and how they contribute to the recently discovered exotic properties of graphene. Our multi-disciplinary approach ensures that the results obtained will not only contribute to the fundamental understanding of correlation effects but also yield valuable input for device physics of graphene."