Interest in drug delivery systems is growing as the delivery of many drugs continues to be a problem due to safety, stability, and compliance issues. This is especially true for the increased number of biologic medicines, which include peptides, proteins, and nucleic acids. Transdermal delivery is an important part of such systems, and the use of physical enhancement methods to penetrate the skin barrier is where the field is headed. This book reviews the strategies available for the delivery of compounds into and through the skin. It also focuses on technological developments in the domain of nanotechnology that can be exploited to enhance the transdermal delivery of drugs.