  We consider the minimal Standard Model as an effective low-energy description
of an unspecified fundamental theory with spontaneously broken conformal
symmetry. The effective theory exhibits classical scale invariance which
manifest itself through the dilaton field. The mass of the dilaton is generated
via the quantum scale anomaly at two-loop level and is proportional to the
techically stable hierarchy between the electroweak scale and a high energy
scale given by a dilaton vacuum expectation value. We find that a generic
prediction of this class of models is the existence of a very light dilaton
with mass between $\sim 0.01$ $\mu$eV to $\sim 100$ MeV, depending on the
hierarchy of scales. Searches for such a light scalar particle may reveal a
fundamental role of conformal invariance in nature.
