  We analyze the dynamical evolution of systems which obey simple growth laws,
like diffusion limited aggregation or dielectric breakdown. We show that, if
the developing patterns is sufficiently complex, a scale invariant noise
spectrum is generated, in agreement with the hypothesis that the system is in a
self organized critical state. The intrinsic noise generated in the evolution
is shown to be independent of the (extrinsic) stochastic aspects of the growth.
Instead, it is related to the complexity of the generated pattern.
