We have developed a new approach for forming lipid nanoparticles (LNP) with and without interfering RNA and DNA from a microfluidic setup. The LNPs are formed by an ionisable cationic lipid, helper lipid, cholesterol and a poly(ethylene glycol) (PEG) lipid, and the different components can self-assemble with the payload via the microfluidic mixing system. These RNA or DNA loaded LNPs mimic those reported in the literature as promising delivery vectors and work by collaborators in MedImmune has demonstrated their high transfection efficacy and low toxicity for different cell lines. Following our DLS and related characterisations, we seek to exploit the unique feature of SANS coupled with contrast variation to determine the inner structures of LNPs, thus relating the plasmid DNA transfection to the LNP inner structures tuned by different help lipids.