These trends were identified and modelled through the use of DoE. From understanding these findings and their interplay in the mechanism of core@shell particle formation, they can be applied to optimise the characteristics of desired SPION@SiO 2 NPs, or can be used to match specifications for a given application or experimental setup. For example, monodisperse SPION@SiO 2 NPs with a yield greater than 70 % which are 50 nm in size could be synthesised using low number of moles of NH 4 OH, and high number of moles of TEOS, over 6 fractionated additions. If altering the size of NPs are of interest, on the other hand, the protocol could be tuned through altering the amount of TEOS and NH 4 OH used, and using 3 fractions of TEOS. Alternatively, the (population) yield and monodispersity of NPs may be increased through using 6 fractionated additions, instead of 3 or 8. This approach has therefore yielded exploitation of the mechanism of formation of the particles to produce a desired goal. It must be emphasised, from the model there are a number of possible routes to the desired result, as observed from the validation experiments, which all produced monodisperse SPION@SiO 2 NPs that had a desired shell thickness of 18 nm, at high populations.