At Kings College London we have recently developed a novel combination formulation, a nanosuspsomicroemulsion (NSME), comprising of a microemulsion (ME) containing one drug and polymer and/or surfactant coated nanoparticles (NS) of a second drug to allow co-administration of two poorly water soluble drugs. The aim of the study is to use SANS in combination with contrast variation to determine the size (in situ) of drug NS contained in the NSME. By contrast matching the ME droplets it will be possible to mask their presence enabling the size and stability of the NP to be determined in situ, something not readily possible by any other technique. The results of the study will be invaluable in establishing whether it is possible to use this novel formulation to deliver combination drug therapy.