  Unveiling the nature of the pseudogap and its relation to both
superconductivity and antiferromagnetic Mott insulators, the pairing mechanism,
and a non-Fermi liquid phase is a key issue for understanding high temperature
superconductivity in cuprates. A number of experimental results gathered
especially in recently years have revealed an unexpected inhomogeneous nature
of cuprates at the nanoscale, indicating the fundamental inapplicability of the
conventional theories based on homogeneous systems. Here we show a microscopic
model of pseudogap and pairing mechanisms on the basis of the consideration of
the spin state around a bound hole in a CuO2 plane and the resulting magnetic
orders, leading eventually to the spin-Peierls distortion responsible for the
Cooper pair formation. The present model fits and accounts for the accumulated
experimental findings reported previously for cuprates, including stripe-like
electronic order, breaking of the rotational symmetry, and the so-called 1/8
anomaly. We believe that the present model can help to develop a complete
theoretical framework applicable to a large family of high-temperature
superconductors, including ferropnictides and ferrochalcogenides.
