  Overlap fermions preserve a remnant of chiral symmetry on the lattice. They
are a powerful tool to investigate the topological structure of the vacuum of
Yang-Mills theory and full QCD. Recent results concerning the localization of
topological charge and the localization and local chirality of the overlap
eigenmodes are reported. The charge distribution is radically different, if a
spectral cut-off for the Dirac eigenmodes is applied. The density q(x) is
changing from the scale-a charge density (with full lattice resolution) to the
ultraviolet filtered charge density. The scale-a density, computed on the Linux
cluster of LRZ, has a singular, sign-coherent global structure of co-dimension
1 first described by the Kentucky group. We stress, however, the cluster
properties of the UV filtered topological density resembling the instanton
picture. The spectral cut-off can be mapped to a bosonic smearing procedure.
The UV filtered field strength reveals a high degree of (anti)selfduality at
"hot spots" of the action. The fermionic eigenmodes show a high degree of local
chirality. The lowest modes are seen to be localized in low-dimensional
space-time regions.
