  Feedback effects due to massive stars and supernovae in the first objects are
shown to strongly regulate both galaxy formation/evolution and the reionization
process. Here we review the most important ones in some detail. We discuss how
Type II supernovae can be used as tracers of the first objects and detected
with NGST, for which we predict supernova number counts including the effects
of gravitational lensing. Preliminary results on the formation of dust in the
ejecta of supernovae of primordial composition are also presented. We finally
turn to the consideration of the process of inhomogeneous reionization due to
primordial stellar sources by means of high resolution numerical simulations,
allowing for a self-consistent treatment of the above feedback processes. These
simulations allow us to draw conclusions on the evolution and epoch of
reionization and about the fate of reionizing objects. We conclude that a large
fraction (~ 99%) of collapsed objects must be dark at redshift around eight.
