  Taking into account four universal constants, namely the Planck's constant
$h$, the velocity of light $c$, the constant of gravitation $G$ and the
Boltzmann's constant $k$ leads to structuring theoretical physics in terms of
three theories each taking into account a pair of constants: the quantum theory
of fields ($h$ and $c$), the general theory of relativity ($c$ and $G$) and
quantum statistics ($h$ and $k$). These three theories are not yet unified but,
together, they underlie the standard models that allow a satisfactory
phenomenological description of all experimental or observational data, in
particle physics and in cosmology and they provide, through the modern
interpretation of quantum physics, fundamental metrology with a reliable
theoretical basis.
