  The evolution of Pulsar Wind Nebulae (PWNe) plays a crucial role in
interpreting the very high energy (VHE; > 10^11 eV) gamma-ray unidentified
sources; and moreover it represents the only viable option to explain the
discovery of several "dark sources" in the TeV gamma-ray (i.e. VHE gamma-ray
sources without lower energies, radio or X-ray counterparts). The newest
time-dependent modeling of PWNe presented in [1] and [2] has to be tested on a
broader sample of young well-known PWNe and applied to the full-sample of "dark
sources". The consequences of this interpretation go far beyond the
interpretation of "dark sources": e.g. there could be strong implication in the
origin of cosmic rays and (when considering a leptonic origin of the gamma-ray
signal) they can be important for reinterpreting the detection of starburst
galaxies in the TeV gamma-ray band.
