  We consider the problem of the nature and possible types of spacetime
singularities that can form during the evolution of \emph{FRW} universes in
general relativity. We show that by using, in addition to the Hubble expansion
rate and the scale factor, the Bel-Robinson energy of these universes we can
consistently distinguish between the possible different types of singularities
and arrive at a complete classification of the singularities that can occur in
the isotropic case. We also use the Bel-Robinson energy to prove that known
behaviours of exact flat isotropic universes with given singularities are
generic in the sense that they hold true in every type of spatial geometry.
