  In string theory, black holes can be made from brane systems that are
partially delocalized in string theory's extra dimensions. It is expected that
they correspond to an ensemble of pure, horizonless microstates sourced by
localized versions of this brane system. This thesis aims at studying the
relationship between supersymmetric black holes and their microstates. In
particular, we apply a concept called local supersymmetry enhancement to
1/4-BPS and 1/8-BPS systems that correspond to two-, three-, and four-charge
black holes. This concept locally increases the number of preserved
supercharges to 16 by adding dipole charges to the system. These bound states
are then expected to be horizonless and describe the microstates of the black
hole. First, we list all dipole charges for 1/4-BPS systems in Type II string
theory. Then, we apply these to generate two structures to enhance 1/8-BPS
systems, one with exclusively internal dipole charges and the other with a
non-trivial shape in the non-compact dimensions. Thus, we identify the dipole
charges for the microstates of various supersymmetric black holes, including
new internal dipole charges for the D1-D5-P black hole and external ones for
the D2-D2-D2-D6 black hole. These dipole charges reveal the local structure of
the black hole's microstates and will be used in the construction of the
corresponding supergravity solutions.
