Vinod P. Shah is a pharmaceutical consultant. He was Scientific Secretary of International Pharmaceutical Federation (FIP) and is now Chair of Regulatory Sciences Special Interest Group of FIP. Dr. Shah has served at the U.S. Food and Drug Administration and has developed several regulatory guidances for the pharmaceutical industry in biopharmaceutics and topical drug products. Dr. Shah is a fellow of FIP as well as the American Association of Pharmaceutical Scientists (AAPS), where he served as president for a year. He is a recipient of an honorary doctorate from Semmelweis University, Budapest, Hungary. Howard I. Maibach is professor of dermatology at the University of California, San Francisco. He received his M.D. at Tulane University Medical School in New Orleans, Louisiana, and completed his residency and research fellowships at the University of Pennsylvania in Philadelphia, Pennsylvania. Professor Maibach is a leading authority in the fields of dermatotoxicology and dermatopharmacology, in which he has conducted research and written extensively. Prof. Maibach has served on the editorial boards of more than thirty scientific journals and is a member of many professional societies, including the American Academy of Dermatology and the International Commission on Occupational Health.John Jenner is a principal scientist at The Defence Science and Technology Laboratory in the UK. He has a degree in pharmacology from the University of Manchester in Manchester, UK, and a Ph.D. from the University of Surrey, Guildford, UK. John has spent his career studying defense against and treatment of highly toxic chemicals. He has an enduring research interest in percutaneously active chemicals, whether toxic materials or drugs, and experience in the design and testing of transdermal formulations. His current interests include the translation of in vitro penetration measurements to in vivo using mathematical modelling.