  We review the main theoretical aspects of the structure formation paradigm
which impinge upon wide angle surveys: the early universe generation of
gravitational metric fluctuations from quantum noise in scalar inflaton fields;
the well understood and computed linear regime of CMB anisotropy and large
scale structure (LSS) generation; the weakly nonlinear regime, where higher
order perturbation theory works well, and where the cosmic web picture
operates, describing an interconnected LSS of clusters bridged by filaments,
with membranes as the intrafilament webbing. Current CMB+LSS data favour the
simplest inflation-based $\Lambda$CDM models, with a primordial spectral index
within about 5% of scale invariant and $\Omega_\Lambda \approx 2/3$, similar to
that inferred from SNIa observations, and with open CDM models strongly
disfavoured. The attack on the nonlinear regime with a variety of N-body and
gas codes is described, as are the excursion set and peak-patch semianalytic
approaches to object collapse. The ingredients are mixed together in an
illustrative gasdynamical simulation of dense supercluster formation.

Astrophysics