  The large-scale structure of the Universe, as traced by the distribution of
galaxies, is now being revealed by large-volume cosmological surveys. The
structure is characterized by galaxies distributed along filaments, the
filaments connecting in turn to form a percolating network. Our objective here
is to quantitatively specify the underlying mechanisms that drive the formation
of the cosmic network: By combining percolation-based analyses with N-body
simulations of gravitational structure formation, we elucidate how the network
has its origin in the properties of the initial density field (nature) and how
its contrast is then amplified by the nonlinear mapping induced by the
gravitational instability (nurture).
