I will discuss what existing data tell us about the reionization of the
Universe and the role played by faint galaxies including some new results
derived by constraining the faint end of the luminosity function at
redshift 6 using a form of surface brightness fluctuations analysis. I
will also discuss expectations for the JWST contribution in this field.
Moving to higher redshift I will discuss how JWST will study the first
galaxies and the constraints it could place on the first stars by studying
their supernovae.