  In quintessential inflationary model, the same master field that drives
inflation becomes, later on, the dynamical source of the (present) accelerated
expansion. Quintessential inflationary models require a curvature scale at the
end of inflation around $10^{-6}M_{\rm P}$ in order to explain the large scale
fluctuations observed in the microwave sky. If the curvature scale at the end
of inflation is much smaller than $10^{-6}M_{\rm P}$, the large scale adiabatic
mode may be produced thanks to the relaxation of a scalar degree of freedom,
which will be generically denoted, according to the recent terminology, as the
curvaton field. The production of the adiabatic mode is analysed in detail in
the case of the minimal quintessential inflationary model originally proposed
by Peebles and Vilenkin.
