Nanoemulsions have the potential in pharmaceutical industries because of the transparency at high droplet volume fraction, higher rate of bioavailability or diffusion and increased shelf life of the pharmaceuticals. Nanoemulsions are clear, thermodynamically stable, isotropic liquid mixtures of oil, water, surfactant and co-surfactant. These are oil-in-water (o/w) type of emulsions with the average droplet size ranging from 5nm to 100 nm. Reduction in droplet size to nanoscale leads to change in physical properties such as optical transparency & unusual elastic behavior. Nanoemulsions have widespread applications in different fields such as pharmaceutics, food technology. Nanoemulsion offers a promising vehicle for increasing the aqueous solubility of poorly water-soluble drugs. Nanoemulsions have many advantages; for instance, enhance drug solubility, perfect thermodynamic stability, ease of manufacturing and permeation over conventional formulations that convert them to important drug delivery systems. The design & development of nanoemulsions aimed at controlling or improving required bioavailability levels of therapeutic agents. This review mainly discussed about the importance of nanoemulsions over other dosage forms, preparation methods, characterization of nanoemulsions and applications.