The phase diagram of La{sub}(2-x)Sr{sub}xCuO{sub}4 is interpreted. From the virial theorem, it is argued that the cross-over from localized to itinerant electronic behavior in the range 0< x < 0.3 is characterized by fluctuations between two equilibrium Cu-O bond lengths. Cooperative local fluctuations give rise to one-hole correlation bags of 5 to 6 copper centers on the underdoped side, to strong-correlation fluctuations in an itinerant-electron matrix on the overdoped side. Spinodal phase segregation between an antiferromagnetic, insulating parent phase and the superconductive phase occurs in the underdoped compositions, between the superconductive phase and the metallic overdoped phase on the other side of the phase diagram. Ordering of the fluctuations into a travelling bipolaronic charge-density/spin-density wave of composition x ≈ 1/6 yields heavy fermions of symmetry (x{sup}2 - y{sup}2) coexisting with light electrons; the high-temperature superconductive pairs are condensed out from the heavy fermions.
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