Book excerpt: A comprehensive and up-to-date overview of the major mineral and organic fillers for plastics, their production, structure and properties, as well as their applications in terms of primary and secondary functions. Edited and co-authored by Professor Marino Xanthos with contributions by international experts from industry and academia, this book presents methods of mixing/incorporation technologies, surface treatments and modifications for enhanced functionality, an analysis of parameters affecting filler performance and a presentation of current and emerging applications. Additionally, the novel classification according to modification of specific polymer properties rather than filler chemical composition provides a better understanding of the relationships between processing, structure and properties of products containing functional fillers and the identification of new markets and applications. For engineers, scientists and technologists involved in the important sector of polymer composites.