The field of chemical abundances and internal mixing of elements in stars has made large progress in the last decade. Both a wealth of new observational data and in the last years also the inauguration of new theoretical roads have been the stimulus for this ESO Workshop held in Castiglione della Pescaia, Italy, 13-17 September 2004. The proceedings cover topics from chemical abundances in the different components of the Milky Way and in local group galaxies, via observational and theoretical papers on mixing in stars to big bang nucleosynthesis and galaxy formation and evolution. As all volumes in this series of ESO Astrophysics Symposia this one gives a comprehensive state-of-the-art overview of the forefront of research in its area. It is thus a valuable reference for both students specializing in the field and researchers alike.