  Over the last decade, an enormous interest and activity in complex networks
have been witnessed within the physics community. On the other hand, diffusion
and its theory, have equipped the toolbox of the physicist for decades. In this
paper, we will demonstrate how to combine these two seemingly different topics
in a fruitful manner. In particular, we will review and develop further, an
auxiliary diffusive process on weighted networks that represents a powerful
concept and tool for studying network (community) structures. The working
principle of the method is the observation that the relaxation of the diffusive
process towards the stationary state is {\em non-local} and fastest in the
highly connected regions of the network. This can be used to acquire
non-trivial information about the structure of clustered and non-clustered
networks.
