Abstract: There is general agreement that the photons that reionize the universe beginning at z ~ 12 are produced by young, starforming galaxies, however, the brighter galaxies that are readily detected at z > 5 fall well short of supplying the required flux of Lyman-continuum photons. I will describe an 8-year spectroscopic search with IMACS on Magellan for the faintest Lyman-alpha emitters (LAEs) at z= 5.7. Our study has pushed the detection limit an order-of-magnitude fainter than the prominent narrow-band-imaging surveys,leading to the first robust measurement of the faint-end-slope of the luminosity function. We find that LAEs make a substantial, perhaps dominant, contribution in the final stages of reionization. These young, low-mass galaxies -- more numerous than today's L* galaxies -- are likely to play an important role in the assembly of early galaxies and their chemical enrichment of the early IGM.