The general characteristics concerning the O/W and W/O as well as droplets and bicontinuous types of microemulsions has been given. The following topics are also discussed: the influence of Winsor parameter R as well as Mitchell and Ninham parameter Sp, on the types of microemulsions and flexibility of their interfaces; the influence of temperature, cosurfactants and concentration of NaCl on optimal solubilization; the dependence of effectiveness of surfactants in preparing of microemulsions on the surfactants structures; the methods of testing of microemulsions and the range of their application.