  We use a novel technique to simulate the growth of the most massive
progenitor of a protocluster region from redshift z~80, when its mass was about
10 Msun until the present day. Our nested sequence of N-body resimulations
allows us to study in detail the structure both of the dark matter object
itself and of its environment. Our effective resolution is optimal at redshifts
of 49, 29, 12, 5 and 0 when the dominant object has mass 1.2e5, 5e7, 2e10, 3e12
and 8e14 Msun/hrespectively, and contains ~1e6 simulation particles within its
virial radius. Extended Press-Schechter theory correctly predicts both this
rapid growth and the substantial overabundance of massive haloes we find at
early times in regions surrounding the dominant object. Although the
large-scale structure in these regions differs dramatically from a scaled
version of its present-day counterpart, the internal structure of the dominant
object is remarkably similar. Molecular hydrogen cooling could start as early
as z~49 in this object, while cooling by atomic hydrogen becomes effective at
z~39. If the first stars formed in haloes with virial temperature ~2000, their
comoving abundance by z=49 would be similar to that of dwarf galaxies today,
while their comoving correlation length would be ~2.5Mpc/h.
