This Ergebnisse volume is devoted to the Uncertainty Principle (UP) and it contains a collection of essays dealing with the various manifestations of this phenomenon. The authors describe different approaches to the subject, using both ''real'' and ''complex'' techniques and succeed to show the influence of the UP in some areas outside Fourier Analysis. The book is essentially self-contained and thus accessible to any graduate student acquainted with the fundamentals of Fourier, Complex and Functional Analysis. As there is no other book approaching the subject of UP in the way Havin and Joericke do in this work, this book will certainly be a welcome addition to the bookshelves of many researchers working in this field.