  The functional consequences of local and global dynamics can be very
different in natural systems. Many such systems have a network description that
exhibits strong local clustering as well as high communication efficiency,
often termed as small-world networks (SWN). We show that modular organization
in otherwise random networks generically give rise to SWN, with a
characteristic time-scale separation between fast intra-modular and slow
inter-modular processes. The universality of this dynamical signature, that
distinguishes modular networks from earlier models of SWN, is demonstrated by
processes as different as spin-ordering, synchronization and diffusion.
