  The geodesic deviation equation (`GDE') provides an elegant tool to
investigate the timelike, null and spacelike structure of spacetime geometries.
Here we employ the GDE to review these structures within the
Friedmann--Lema\^{\i}tre--Robertson--Walker (`FLRW') models, where we assume
the sources to be given by a non-interacting mixture of incoherent matter and
radiation, and we also take a non-zero cosmological constant into account. For
each causal case we present examples of solutions to the GDE and we discuss the
interpretation of the related first integrals. The de Sitter spacetime geometry
is treated separately.
