Lipid dosage forms are attractive delivery systems for hydrophobic drug molecules. Emulsion is one of the popular system since many decades. Pharmaceutical applications of emulsions widened especially after micro emulsion emergence. Now a day Microemulsion is an emerging trade and having worldwide importance in a variety of technological applications. These applications include enhanced oil recovery, combustion, cosmetics, pharmaceuticals, agriculture, metal cutting, lubrication, food, enzymatic catalysis, organic and bio-organic reactions, chemical synthesis of nanoparticles etc. This review article deals with feature and application of microemulsion. a brief introduction and definition, structure, type, formation characteristics, stability, phase behavior and the effect of additives, pressure, temperature on the phase behavior of microemulsion . In addition to oral and intravenous delivery, they are amenable for sustained and targeted delivery through ophthalmic, dental, pulmonary, vaginal and topical routes. Microemulsions are experiencing a very active development as reflected by the numerous publications and patents being granted on these systems. They have been used to improve the oral bioavailability of various poorly soluble drugs including cyclosporine. Keywords: Microemulsion, Self micro emulsifying system, poor soluble, thermodynamically stable, Sustained & Controlled release, Drug delivery.

Nebivolol HCl is a newer drug of β1-adrenergic blocker category, basically used as anti-hypertensive. It is a 3rd generation, antagonist, having NO (nitric oxide) enhancing vasodilator properties. It has 12% oral bioavailability, because of its pre systemic metabolism by the means of cytochrome P450 2D6 enzymes. Its log P value is 4.03 and 5mg is its daily dose. It is highly lipophilic drug and belongs to class BCS II, with slow dissolution. Bioavailability of any drug can be improved by avoiding its first pass metabolism and promoting solubility.  Several researchers have worked on the development of ME formulations on different poor water-soluble drugs, to increase their solubility. The purpose of this study is an attempt to enhance the solubility to improve the bioavailability of nebivolol drug by developing a novel delivery system that is microemulsion (ME) .ME formulations were developed using different oil, surfactant and co-surfactants in different ratio and studied on various parameters. Different preformulation tests done on received sample of Nebivolol. FTIR study was performed in order to find out any interactions between the ingredients. Based on the solubility Capmul Pg-12 was finalized oil, Tween 80 as surfactant, propylene glycol as the cosurfactant based on solubility and emulsification efficiency. Five Nebivolol ME formulations were successfully developed by use of oil, water, SA and Co-SA different ratio. Prepared formulations were studied for different properties- transmittance (%), pH, refractive index, viscosity, drug content, and solubility. It was seen that after 4 hours of diffusion, the drug released from the formulation ME5 is faster and more than that of the other i.e., 90.2±0.06%. It was found that ME5 was more stable and Soluble than other prepared formulations. With the better solubilty the bioavailability of Nebivolol will increased and helps in faster absorption and High diffusion in systemic circulation with lower or no risk of degradation. It somehow also reduced frequent intake of drug. Keywords: Nebivolol, micro emulsion, Ternary phase diagram, surfactant, co-surfactant.