The idea of editing this book was born in the winter of 1988/1989. Christian Endler was organizing the workshop 'Wasser und Information' (water and information) in Austria [1], and Jürgen Schulte was working on a publication of his results on atomic cluster stabilities and long-range electromagnetic interaction in atomic clusters. It was Franz Moser from the Technical University of Graz who brought these two together. After a talk that Moser had given in Bremen, Schulte explained to hirn his ideas about clusters and long range interaction, and his concern about reliable theories and experiments in research on ultra high dilutions (UHD) and homoeopathy. He was suggested to be a speaker at the Austrian workshop. Reviewing the contributions of this workshop and the current literature on UHD and homoeopathy, especially the PhD thesis by Giesela King [2] and the excellent survey by Marco Righetti [3], we decided to work on a book in order to critically encou­ rage more scientists to work and publish in this field with a high scientific standard. What we had in mind was a useful contribution to the goal to lift research on UHD and homoeo­ pathy to an internationally acceptable scientific standard, to encourage international scien­ tists to work in this area and to establish UHD and homoeopathy in academic science. Delayed by our individual academic careers in our specific fields, and delayed by lack of funds it took us about four years to finish this book.