Abstract: 
Properties of isolated and aggregated nanoparticles in fundamental and applied research are reviewed. Recent progress in the synthesis, functionalization, characterization, and detection of nanoparticles is presented. Variable size and shape nanoparticles of well-defined internal structure are prepared by colloidal chemistry approaches. Most important for interactions with their environment is the surface functionalization, where the ligand shell plays a crucial role. The stability of isolated nanoparticles in biological media as well as the uptake of nanoparticles into cells and skin is reviewed, which also includes the use of advanced diagnostics, such as X-ray microscopy and tomography as well optical near-field microscopy by employing tunable infrared radiation from synchrotron radiation sources. Besides biomedical studies on nanoparticles and nanoscopic drug delivery systems photonic applications of nanomaterials are discussed. This includes size-dependent properties of single nanoparticles as well as ordered arrays of nanoscopic building blocks, in which nanoplasmonic processes and the formation of high harmonics are studied. These systems serve ultimately as perspective short wavelength photon sources reaching into the attosecond time regime.