  Understanding the mechanism of high transition temperature (Tc)
superconductivity in cuprates has been hindered by the apparent complexity of
their multilayered crystal structure. Using a cryogenic scanning tunneling
microscopy, we report on layer-by-layer probing of the electronic structures of
all ingredient planes (BiO, SrO, CuO2) of Bi2Sr2CaCu2O8+{\delta} superconductor
prepared by argon-ion bombardment and annealing technique. We show that the
well-known pseudogap (PG) feature observed by STM is inherently a property of
the BiO planes and thus irrelevant directly to Cooper pairing. The SrO planes
exhibit an unexpected Van Hove singularity near the Fermi level, while the CuO2
planes are exclusively characterized by a smaller gap inside the PG. The small
gap becomes invisible near Tc, which we identify as the superconducting gap.
The above results constitute severe constraints on any microscopic model for
high Tc superconductivity in cuprates.
