  In this paper we construct the BPS black hole generating solution of
toroidally compactified string (and M) theory, giving for it both the
macroscopic and microscopic description. Choosing a proper U-duality gauge the
latter will be given by a bound state made solely of D-branes. The axionic
nature of the supergravity solution will be directly related to non-trivial
angles between the constituent D-branes (type IIB configuration) or, in a
T-dual gauge, to the presence of magnetic flux on constituent D-brane world
volumes (type IIA configuration). As expected, the four dimensional axion
fields arise from the dimensional reduction of non-diagonal metric tensor
components or Kalb-Ramond B field components for type IIB or type IIA cases,
respectively. Thanks to this result it is then now possible to fill the full
56-dimensional U-duality orbit of N=8 BPS black holes and to have a macroscopic
and microscopic description of all of them.
