Pseudogap phase in high-T-c superconductors

We describe the approach of the superconducting state as a sequence of cros sover phenomena. As the temperature is decreased, uncorrelated pairing of t he electrons leads to the opening of a pseudogap at T*(F). Upon further low ering the temperature those electron pairs acquire well behaved itinerant f eatures at T*(B), leading to partial Meissner screening and Drude-type beha vior of the optical conductivity. Further decrease of the temperature leads to their condensation and superconductivity at T-e. The analysis is done o n the basis of the boson-fermion model in the crossover regime between 2D a nd 3D.