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The 4f(5f) electrons in the rare earth(uranium) atom are pushed deep into the interior of the closed 5s(6s) and 5p(6p) shells because of the strong centrifugal potential 1(1+1)/r2 , where 1=3 holds for the f electrons. This is a reason why the 4f (5f) electrons possess an atomic-like character even in the compound. On the other hand, the tail of their wave function spreads to the outside of the closed 5s(6s) and 5p(6p) shells, which is highly influenced by the potential energy, the relativistic effect, the distance between the rare earth(uranium) atoms, and hybridization of the 4f(5f) electrons with the conduction electrons. These cause the various phenomena such as valence and spin fluctuations, gap states, Kondo lattice, heavy electrons (fermion), metamagnetism and superconductivity for the f electron compounds.1