  A brief review of microscopic studies of high-Tc superconductors HgBa2CuO4+d
and HgBa2CaCu2O6+d is presented. The topics concerned are the pseudo spin-gap,
the antiferromagnetic spin fluctuations near the quantum critical point, and
the mechanism of the high Tc via NMR. The crystal structure with the flat CuO2
plane, two-dimensional electrical resistivity, Cu NQR, NMR experimental results
are discussed.
