In October 2007, the U.S. National Academies and the Iranian Institute for Advanced Studies in Basic Science organized the first of a series of planned U.S.-Iranian workshops on the topic 'Science as a Gateway to Understanding'. This new workshop series is a component of the broader effort of the National Academies to support bilateral workshops and exchange visits in a variety of fields with a number of Iranian institutions that began in 2000. This book includes papers that were presented at the workshop and summaries of the discussions that followed some of the presentations. At the conclusion of the workshop there was general agreement that the presentations on many aspects of science and scientific cooperation that have a bearing on mutual understanding were an important first step. Several participants underscored that the next workshop should emphasize how scientific cooperation can lead in concrete terms to improved understanding among both academic and political leaders from the two countries.