Modern drug discovery technique led to the consistent increase in the number of new pharmacologically active lipophilic compounds that are poorly water soluble. A great challenge facing the pharmaceutical scientist is making these molecules into orally administered medications with sufficient bioavailability. One of the most popular approaches to improve the oral bioavailability of these molecules is the utilization of a lipid based drug delivery system. Development and optimization of formulation is an integral part of manufacturing and marketing of any therapeutic agent which is indeed a time consuming and costly process. Optimization process may require alteration in formulation composition, manufacturing process, equipment and batch sizes. If these types of changes are applied to a formulation, studies in human healthy volunteers may be required to prove that the new formulation is bioequivalent with the old one.IVIVC includes in vivo relevance to in vitro dissolution specifications and can serve as surrogate for in vivo bioavailability and to support biowaivers. This book provides the information about the use of biorelevant media as media an alternative for in vivo studies.