This book contains the proceedings of the meeting held in the lovely island of Vulcano, close to the noth coast of Sicily (ltaly) on September 20-24, 1999. Vlllcano is one of the group called Eolian islands. The name derives from the fact that the island is a volcano, and legend says that it was inhabited by the greek god Volcano. The subject of the conference was "The Chemical Evolution of the Milky Way: Stars versus Clusters." This colIoquium was a project devised by a group of italian astronomers (Franco Giovannelli, Francesca Matteucci and Sergio Or tolani) together with Beatriz Barbuy (Brazil) and R. M. Rich (U. S. A. ), on the hasis of the fact that alI of them actively work in the field and that the last meeting, held in Italy on this subject, was the Elba meeting in 1989 on "Chem ical and Dynamical Evolution of Galaxies." The reason for having the meeting in Vulcano was that the Istituto di Astrofisica Spaziale (Tor Vergata, Roma) has a long tradition of organizing astronomic al meetings in Vulcano at the pleasant Eolian Hotel, which provides a secluded, beautiful and relaxing environment. The main purpose of this workshop was to gather a representative communi ty of astrophysicists involved in the study of the chemical evolution of the Milky Way both from a theoretical and an observational point of view."

Gas at temperatures exceeding one million degrees is common in the Universe. Indeed it is likely that most of the gas in the Universe exists in intergalactic space in this form. Such highly-ionized gas, or plasma, is not restricted to the rarefied densities of intergalactic space, but is also found in clusters of galaxies, in galaxies themselves, in the expanding remnants of exploded stars and at higher densities in stars and the collapsed remains of stars up to the highest densities known, which occur in neutron stars. The abundant lower-Z elements, at least, in such gas are completely ionized and the gas acts as a highly conducting plasma. It is therefore subject to many cooperative phenomena, which are often complicated and ill-understood. Many of these processes are, however, well-studied (if not so well-understood) in laboratory plasmas and in the near environment of the Earth. Astronomers therefore have much to learn from plasma physicists working on laboratory and space plasmas and the parameter range studied by the plasma physicists might in turn be broadened by contact with astronomers. With that in mind, a NATO Advanced Research Workshop on Physical Processes in Hot Cosmic Plasmas was organized and took place in the Eolian Hotel, Vulcano, Italy on May 29 to June 2 1989. This book contains the Proceedings of that Workshop.

Space experiments have opened practically all electromagnetic windows on the Universe. A discussion of the most important results obtained with multi-frequency photonic astrophysics experiments will provide new input to advance our knowledge of physics, very often in its more extreme conditions.
A multitude of high quality data across the whole electromagnetic spectrum came at the scientific community's disposal a few years after the beginning of the Space Era. With these data we are attempting to explain the physics governing the Universe and its origin, which continues to be a matter of the greatest curiosity for humanity.
In this book we describe the latest steps of the investigations born with the advent of space experiments. We highlight the most important results, identify unsolved problems, and comment on perspectives we can reasonably expect.
This book aims to provide a useful tool for the reader who is not specialized in space astrophysics and for students. Therefore, the book is written in the form of a review with a still reasonable length, taking into account the complexity of the arguments discussed. We do not claim to present a complete picture of the physics governing the Universe, but have rather selected particular topics for a more thorough discussion. A cross section of essays on historical, modern, and philosophical topics is offered and combined with personal views into tricks of the space astrophysics trade.

This review of the most up-to-date observational and theoretical information concerning the chemical evolution of the Milky Way compares the abundances derived from field stars and clusters, giving information on the abundances and dynamics of gas.