Objective The aim of this review is to introduce the self-emulsifying drug delivery systems which can be used to improved the bioavailability of poorly water soluble drug substances. Methods The review summarizes the most prominent results of the lipid based medicinal preparations, such as microemulsions and nanoemulsions developed in the last two decades. Results The analysis of the references details the lipid based formulation classification systems, the most common excipients, the quality attributes depending on the ingredients, as well as the differences in the characteristics of micro- and nanoemulsions. Conclusions The summary demonstrates the formulation possibilities of self-emulsifying drug delivery systems, which may increase the applicability and are promising to improve the therapeutic effectiveness.