In September 2002, a NATO-ASI was held in Cetraro (CS), Italy on the theme of "Metal-Ligand Interactions in Molecular-, Nano-, Micro-, and Macro-systems in Complex Environments". This event has followed the previous ones held in the same place in 1991, 1994 and 1998. In the present and the previous schools a broad interdisciplinary cross-section of experimental and theoretical researchers, interested in a better understanding of metal-ligand interactions from different viewpoints, was linked together to exchange experience, to review the state-of-the-art, to indicate new techniques and methods, to explore new fields and perspectives. Particular emphasis was given to the problems related with the crossing from molecular systems to nano-, macro-and micro-scale materials and to the effects of the environment on the properties of the molecular systems. The school was organized around lectures and special research seminares given by leading experts in the following fields: . metal clusters . inorganic complexes and materials . surface phenomena . adsorption and catalysis . organic and bio-inorganic systems . ab initio theory . density functional theory . classical and quantum dynamics This volume contains the formal lectures and selected contributed papers and describes the main aspects and problems tackled during the 12 days of the event.