  This pedagogical review is devoted to quintessential inflation, which refers
to unification of inflation and dark energy using a single scalar field. We
present a brief but concise description of the concepts needed to join the two
ends, which include discussion on scalar field dynamic, conformal coupling,
instant preheating and relic gravitational waves. Models of quintessential
inflation broadly fall into two classes, depending upon the early and late time
behavior of the field potential. In the first type we include models in which
the field potential is steep for most of the history of the Universe but turn
shallow at late times, whereas in the second type the potential is shallow at
early times followed by a steep behavior thereafter. In models of the first
category inflation can be realized by invoking high-energy brane-induced
damping, which is needed to facilitate slow roll along a steep potential. In
models of second type one may invoke a non-minimal coupling of the scalar field
with massive neutrino matter, which might induce a minimum in the potential at
late times as neutrinos turn non-relativistic. In this category we review a
class of models with non-canonical kinetic term in the Lagrangian, which can
comply with recent B mode polarization measurements. The scenario under
consideration is distinguished by the presence of a kinetic phase, which
precedes the radiative regime, giving rise to blue spectrum of gravity waves
generated during inflation. We highlight the generic features of quintessential
inflation and also discuss on issues related to Lyth bound.
