At surfaces and interfaces the magnetic order and magnetization dynamics is modified due to the lack or change of nearest-neighbor coordination. As an example it will be shown, how in thin film or nanoparticle systems the surface or interfaces influence the superparamagnetic behavior and the electronic structure. For instance, in FePt nanoparticles surface anisotropy is dominating and related to the chemical state of the surface atoms. Furthermore, the electronic structure of the metallic core is strongly influenced by surface states. This leads to size dependent features. Besides the scientific interest in the properties of such technical nanostructures and materials there is a link to magnetoreception in biology, i.e. to highly sensitive magnetic nanostructures in homing pigeons.