  In this paper, we present an overview of some of the existing issues of the
research in quantum gravity. We also introduce the basic ideas that led
Padmanabhan to consider a duality property in path integrals. Such a duality is
consistent with the T-duality in string theory. More importantly, the path
integral duality discloses a universal feature of any quantum geometry, namely
the existence of a zero point length $L_0$. We also comment about recent
developments aiming to expose effects of the zero point length in strong
electrodynamics and black holes. There are reasons to believe that the main
characters of the phenomenology of quantum gravity may be described by means of
a single parameter like $L_0$.
