In this book author focus on importance of lipids for drug delivery of poorly soluble and poorly permeable drugs. In the pharmaceutical filed most of the active constituents are poorly soluble which a challenging task to deliver orally. To overcome this challenge various solid lipids and liquid lipids were utilized to formulate novel formulations like solid lipid nanoparticles and nanostructured lipid carriers. This type of novel formulations will help to permeate BCS class II drug through lymphatic route and avoid hepatic first pass metabolism which ultimately improve bioavailability. This book covers mechanism of absorption from lipid based formulations, types of various lipid based drug delivery as well as conversion of liquid lipid dispersion in to solid form for ease of administration.