Magnetic materials are one of the most important pillars of our nowadays society. Without these materials – the fundament of modern microelectronics - we would have to write this abstract by hand. Coexisting with electricity, magnetic phenomena are exploited in data storage devices, control systems, sensors and music instruments. However, if it comes to the nano regime, magnetism is rather unexplored. While we gain more and more information on the influence of external fields on e.g. the orientation of magnetic nanoparticles during drying processes, the influence of magnetic fields on magnetic thin film formation and their potential for growth control during thermal CVD is not investigated yet. By a combination of external magnetic fields and conventional CVD, we created a specialized setup, which allows the investigation of magnetic field effects on thin film formation, delivering an additional possibility to transfer molecular properties to nano scaled materials. Depending on the oxidation state of the central atom in the precursor, an interaction between clustered molecules and an applied magnetic field, depending on the number of unsaturated electronic spins and cluster size can be studied. While decomposing during CVD process, small clusters are formed, which - if consisting of a magnetic material - might interact with an applied external magnetic field. In this presentation, external magnetic field effects on the growth behaviour of ferromagnetic materials like Fe will be addressed and first results on the formation of transition metal oxides discussed.