A great number of new drug candidates identified from the discovery pipeline are poorly water soluble, which is a drawback to bring such candidates into the pharmaceutical market. Formulating these compounds as self-emulsifying/microemulsifying/ nanoemulsifying drug delivery systems (SEDDS/SMEDDS/SNEDDS) within lipid based formulations is of growing interest. Some of the recent studies have resulted in commercial products that provided improved bioavailability and dissolution due to the better dispersion properties of SEDDS/SMEDDS/SNEDDS. An ongoing challenge that the pharmaceutical industry is facing is identifying in vitro tests that are needed in order to predict the behavior of dosage forms in the GI tract. The goal of the current review is to present the various levels of in vitro-in vivo correlations (IVIVCs) and to provide tools on the utilization of the IVIVCs in product development and optimization of SEDDS/SMEDDS/SNEDDS.