Nanoemulsions are kinetically stable liquid-in-liquid dispersions with droplet sizes on the order of 100 nm. They have useful properties such as high surface area per unit volume, robust stability, optically transparent appearance, and tunable rheology. Nanoemulsions are used in various applications including drug delivery, food, cosmetics, pharmaceuticals, and material synthesis. They serve as model systems to understand nanoscale colloidal dispersions. Nanoemulsions can be prepared using high-energy methods like high pressure homogenization and ultrasonication, or low-energy methods like phase inversion temperature and emulsion inversion point. Recent methods include bubble bursting and evaporative ripening. This review summarizes the major methods to prepare nanoemulsions, theories to predict droplet size, physical conditions and chemical additives that affect droplet stability, and recent applications. Nanoemulsions are kinetically stable, meaning they can remain stable over long time scales. They are less sensitive to physical and chemical changes compared to thermodynamically stable microemulsions. The review discusses the formation of nanoemulsions, droplet size control, destabilization mechanisms, and their properties and applications. Nanoemulsions have unique properties such as small droplet size, exceptional stability, transparent appearance, and tunable rheology. These properties make them attractive for applications in the food, cosmetic, pharmaceutical industries, and drug delivery. They can also serve as building blocks for advanced materials. Nanoemulsions are used in drug delivery for various modes including topical, ocular, intravenous, intranasal, and oral delivery. They are also used in the food industry to design smart foods with ingredients that are otherwise difficult to incorporate due to low-water solubility. Nanoemulsions have been used as ultrasound imaging agents and for targeted therapeutics. They have also been used in the development of multifunctional nanoemulsion platforms for imaging-guided therapy. The review highlights the importance of controlling droplet size and stability in nanoemulsions for various applications.Nanoemulsions are kinetically stable liquid-in-liquid dispersions with droplet sizes on the order of 100 nm. They have useful properties such as high surface area per unit volume, robust stability, optically transparent appearance, and tunable rheology. Nanoemulsions are used in various applications including drug delivery, food, cosmetics, pharmaceuticals, and material synthesis. They serve as model systems to understand nanoscale colloidal dispersions. Nanoemulsions can be prepared using high-energy methods like high pressure homogenization and ultrasonication, or low-energy methods like phase inversion temperature and emulsion inversion point. Recent methods include bubble bursting and evaporative ripening. This review summarizes the major methods to prepare nanoemulsions, theories to predict droplet size, physical conditions and chemical additives that affect droplet stability, and recent applications. Nanoemulsions are kinetically stable, meaning they can remain stable over long time scales. They are less sensitive to physical and chemical changes compared to thermodynamically stable microemulsions. The review discusses the formation of nanoemulsions, droplet size control, destabilization mechanisms, and their properties and applications. Nanoemulsions have unique properties such as small droplet size, exceptional stability, transparent appearance, and tunable rheology. These properties make them attractive for applications in the food, cosmetic, pharmaceutical industries, and drug delivery. They can also serve as building blocks for advanced materials. Nanoemulsions are used in drug delivery for various modes including topical, ocular, intravenous, intranasal, and oral delivery. They are also used in the food industry to design smart foods with ingredients that are otherwise difficult to incorporate due to low-water solubility. Nanoemulsions have been used as ultrasound imaging agents and for targeted therapeutics. They have also been used in the development of multifunctional nanoemulsion platforms for imaging-guided therapy. The review highlights the importance of controlling droplet size and stability in nanoemulsions for various applications.