Quantum confinement, a basic quantum mechanic feature, becomes increasingly important in Nano Science. The optimisation of quantum confinement effects of semiconductor quantum dots (outlined in more detail in lecture N5) is closely related to surface and interface properties of optical active nanostructures both in semiconductor hetero structures and colloidal nanoparticles in solution. Since the number of surface atoms is of comparable magnitude as the core atoms, physico-chemical properties depend drastically on the kind of surface and the related formation and reconstruction dynamics. Such properties are investigated by techniques such as optical spectroscopy, X-ray crystallography, magnetic resonance or electron microscopy. Of central importance are techniques based on the optical detection of single quantum dots.