The book gives an updated overview of the recent developments within organometallic catalysts for olefin polymerization. It covers the whole field from the preparation of organometallic precursors to the polymerization process itself. Recent developments in Group IV metallocenes, complexes of other transition elements with a variety of different ligands, and traditional heterogeneous Ziegler-Natta and chromium-based catalysts are described. The book also includes the recent developments of new co-catalysts. A special chapter discusses the recent developments on the mechanistic understanding on the molecular level of the polymerization process using different catalysts. Another chapter deals with polymerization and copolymerization studies where non-traditional co-monomers have also been used. Finally, the polymerization process is discussed in terms of heterogenization of catalysts and particle microreactor effects.