Nanoemulsions, usually spherical, are a group of dispersed particles used for pharmaceutical and biomedical aids and vehicles that show great promise for the future of cosmetics, diagnostics, drug therapies and biotechnologies. They exist in a wide variety of forms that are dictated by the particle components. Nanoemulsions are generally considered to be in the size range of less than and around 100 nm in diameter. The particles can exist as water-in-oil and oil-in-water forms, where the core of the particle is either water or oil, respectively. More complex variations also exist but these are often larger. The longer-term properties of the particle are dependent on the composition of the adsorbed material lying at the dispersed droplet interface with the dispersion medium. This has an impact on the partitioning and extraction of droplet contents. Thermodynamically stable particles are characterized by having a very low surface tension and this produces a very large surface area. Nanoemulsions can also include small meta-stable very small-scale emulsions; here the surface properties and chemistry can strongly influence behaviour. Processing, storage and formulation composition can also have an impact on the longevity of a pharmaceutical preparation. Some revolutionary new nanoemulsion droplets based on fluorinated compounds are finding a number of widespread biomedical roles and applications. Developments in nanoemulsion technology are likely to lead to a much greater use of this medium in future pharmaceuticals.