Nanoemulsions are composed of nanoscale droplets of one immiscible liquid dispersed within another, which have been the focus of extensive research due to their capacity to solubilize and deliver both hydrophobic and hydrophilic active compounds with unique physical properties. In broad sense, submicron emulsions, microemulsions, self-microemulsifing drug delivery systems and cholesterol-rich microemulsions all belong to nanoemulsions. This review starts with a brief introduction to the definition, formulation rationale, and types of nanoemulsions, and focuses on the absorption, disposition, pharmacokinetics properties of nanoemulsions via different administration routes such as the oral, intravenous, transdermal, ocular, nasal and rectal routes.