  In many composites the electrical transport takes place only by tunneling
between isolated particles. For a long time it was quite a puzzle how, in spite
of the incompatibility of tunneling and percolation networks, these composites
conform well to percolation theory. We found, by conductance atomic force
microscopy measurements on granular metals, that it is the apparent cut-off of
the tunneling to non-nearest neighbors that brings about this behavior. In
particular, the percolation cluster is shown to consist of the
nearest-neighbors sub-network of the full tunneling network.
