Percolation is one of the most prominent problems in statistical physics. Theoretical studies of
percolation and the application of percolation models in diverse scientific disciplines have resulted
in thousands of papers over the last decades. The talk focuses on the electric transport properties
of isotropic and directed percolation clusters as explained by the renormalization group. For studying
these properties we consider simple and intuitive models, viz. the random resistor network, a bond
percolation model where open bonds function as insulators and occupied bonds function as resistors,
and the random diode network, where occupied bonds function as diodes. We explain the field theoretic
formulation of these models and sketch their diagrammatic perturbation theory. It turns out that the
Feynman diagrams for these models can be interpreted as if they were real networks: they consist of
insulators and respectively resistors or diodes, they carry currents and so on. Being interested in
a certain property of a real network we essentially just have to determine the corresponding property
of the Feynman diagrams. For example, the resistance of the Feynman diagrams provides us with the
average resistance of the real networks etc. We review some of the results obtained by exploiting
this real world interpretation and compare them to numerical results.