This book contains the papers presented at the "First International Sympo st sium on Aerogels (1 ISA)," held in September 1985 at. the University of Wiirzburg, Fed. Rep. of Germany. It was the first meet.ing of this kind, wit.h participants from several European count.ries, the United States of America, Canada, South America, and Africa. The meeting was interdisciplinary, with most of the participants being physicists, chemists or material scientists ei ther from universities or from industrial research institutes. Let me try to shed some light upon the class of substances the symposium was...