An advanced mode of drug delivery system has been developed to overcome the major drawbacks associated with conventional drug delivery systems. Nanoemulsions are submicron sized emulsion that is under extensive investigation as drug carriers for improving the delivery of therapeutic agents and drug targeting. These are the thermodynamically stable isotropic system in which two immiscible liquid (water and oil) are mixed to form a single phase by means of an appropriate surfactants or it mixes with a droplet diameter approximately in the range of 0.5–100 um. Nanoemulsion droplet size falls typically in the range of 20–200 nm and shows a narrow size distribution. Nanoemulsion show great promise for the future of cosmetics, diagnostics, drug therapies and biotechnologies. These are the thermodynamically stable isotropic system in which two immiscible liquids are mixed to form a single phase by means of an emulsifying agent, i.e., surfactant and co-surfactant. The droplet size of nanoemulsion falls typically in the range 20–200 nm. The main difference between emulsion and nanoemulsion lies in the size and shape of particles dispersed in the continuous phase. In this review, the attention is focused to give a basic idea about its formulation, method of preparation, characterization techniques, evaluation parameters, and various applications of nanoemulsion.