Based on knowledge of the chemical reactions and morphology, significant changes can be made in the morphology of a toughened dicyanate thermosetting resin through the intelligent manipulation of the cure cycle and real-time knowledge of the conversion of the system. Fourier transform near infra-red spectroscopy using fibre-optic sensors was employed to follow such reactions. Various cure cycle changes resulted in similar degree of cure, thermal stability and solvent resistance, but yielded a 20% change in neat resin toughness associated with the morphologies. The morphological variety was shown not only to occur within reasonable cure cycle variations for neat resin, but were also induced through a processing change in a graphite-reinforced composite containing this resin. Design of custom or gradient morphologies to provide specific mechanical properties is now feasible with this technology. These same approaches could be adapted to the custom manufacture of optical and/or damping properties. This manipulation is not limited to the processing of toughened thermosetting resins.