This volume focuses on isotopic signatures of volatile elements as tracers for evolutionary processes during the formation of the Sun and the planets from an interstellar molecular cloud and, in turn, illuminates how the isotopic compositions of contemporary solar system objects have been established. The book is an integrated collection of articles by experts in planetary science, solar and plasma physics, astrophysics, mineralogy and chemistry that met for an interdisciplinary workshop at the International Space Science Institute in Bern in January 2002. The authors present analyses of isotope abundance ratios for volatile elements in the sun, planets, satellites, comets, meteorites and interplanetary dust particles, as well as a review of isotopic ratios in star-forming interstellar clouds. This provides insight into the physical and chemical processes in the pre-solar molecular cloud that collapsed to form the Sun and the solar accretion disk. Furthermore, information is presented on dynamical processes and conditions inside this protoplanetary disk, in particular the degree of reprocessing of interstellar solid material, the formation of solids inside the disks, and the formation of terrestrial and giant planets and their satellites. Isotopic fractionation processes discussed in this book include chemical reactions such as ion-molecule and photochemical reactions, nuclear processes inside the sun and in its atmosphere, plasma processes, gravitational escape of gases from planetary atmospheres exposed to the solar wind and solar radiation, thermodynamic processes, a variety of accretion and adsorption processes and mixing of material from the interstellar environment with the material of the evolving solar system. The volume is intended to provide active researchers in the fields of planetary science and space physics with an up-to-date status report on the topic, and also to serve graduate students with introductory material into the field.