Emulsions are liquid–liquid dispersions with one liquid phase dispersed in the other liquid phase as small droplets. Nano-emulsions consist of fine oil-in-water dispersions, having droplets covering the size range of 100–600nm. Nano-emulsions are also referred to as mini-emulsions. Nanoemulsions have great potential applications in pharmaceutics, foods and cosmetics due to their attractive properties. Nanoemulsion is a dispersion consisting of oil, surfactant and an aqueous phase, which is an isotropically clear and thermo-dynamically or kinetically stable liquid solution. One often most promising technology is the nanoemulsion drug delivery system, which is being applied to enhance the solubility and bioavailability of lipophilic drugs. The nanosized droplets leading to an enormous increase in interfacial areas associated with nanoemulsion would influence the transport properties of the drug. Correspondingly, an over view of characterisation technologies to differentiate between the micro and nanoemulsions alongside their benchmarks in terms of their physical and thermodynamic stabilities, is also described in this review.