not, however, exhausted the field, boredom has not set in, and unexpected applications continue to appear. In the present volume, Uli Gonser has collected contributions that display the "exotic" side of the Mossbauer effect. They range from a masterly de­ scription of the red-shift experiment to a clear exposition of a powerful solution to the old and painful phase problem in crystallography. Each of the contributions exhibits a different side of recoilless gamma-ray emission. Together they show that the field is very much alive and continues to delight us with elegant solutions to old problems, unanticipated glimpses at new phenomena, clever uses of new technical possibilities, and ingenious applications to fields far away from physics. I believe that novel features of the Mossbauer effect will continue to appear and that new applications will still be found.