[en] The long-term quest for f-orbital participation in bonding is described along with progress in organometallic chemistry of f-block elements. A wide variety of sigma-bonded organolanthanide compounds have been synthesized with the expectation of the f-orbital participation in metal-carbon bonding. To our disappointment, visible spectra, magnetic properties and x-ray analyses did not show any definite evidence of f-orbital participation in bonding. However, recent ESCA studies have revealed unique electronic structures of a series of f-block phthalocyanine and porphyrin complexes in which f-orbitals play an important role in the core ionization process