Abstract: Reionization marks the last major phase transition of matter in the Universe and its completion had crucial impact on the formation of the smallest galaxies. While reionization roughly encapsulated the first Gyr of cosmic time, the precise timing, topology and the sources of ionizing photons are unknown. Did reionization proceed rapidly or gradually and was it driven by rare bright galaxies, or numerous faint ones? In my talk I will present the first JWST results from the EIGER survey, which is a large program that is blindly searching for emission-line galaxies in the foreground, vicinity and background of the brightest quasars in the early Universe (z~6-7). I will show how we confirmed redshifts for >100 galaxies in the first ~500 Myr of cosmic time, and simultaneously measured the mass - metallicity for the first time using efficient NIRCam grism observations. We demonstrate that Lya transmission spikes in the quasar spectrum at z~6 are detected preferentially at characteristic distances of a few cMpc from galaxies. Finally, I will highlight how to address current limitations in addressing the role of galaxies in reionizing the Universe with new and future VLT programs, and how the MUSE eXtremely Deep Field already provides a glimpse of how we can obtain tomographic studies of (re)ionized bubbles at the end stages of cosmic reionization with future ELT spectroscopy.
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