Nanoparticles are particles which are smaller than 150 nm in diameter. Due to their large surface they have different properties compared to the respective bulk material. Today nanoparticles are already used for various applications, e.g. in cosmetics or as catalysts. Concerning their application in the brain they are considered as contrast agents for magnetic resonance imaging, as carriers for drug delivery, for labeling of cells or for elimination of tumors. In order to improve the knowledge on potential consequences of an exposure of brain cells with nanoparticles, we study the biocompatibility, the cellular uptake, the intracellular trafficking and the fate of the nanoparticles in brain cells.