While the lanthanides (strictly defined as the 14 elements following lanthanum in the periodic table, but as normally used also include lanthanum itself) have several unique characteristics compared to other elements, their appearance in the history of the development of organometallic chemistry is rather recent. Since the f orbitals are filled gradually from lanthanum ([Xe]4f ) to lutetium ([Xe]4fl4), they are regarded as the f-block elements, which are discriminated from the d-block transition elements. This book was edited as the second volume of "Topics in Organometallic Chemistry",...