Abstract
Studying galaxies at ultra-high redshifts (z > 6) provides a unique insight into the early stages of galaxy formation and evolution. I will give an overview of how star-forming Lyman-break galaxies are selected in the first billion years, and what is known about their properties from multi-wavelength follow-up (e.g. from ALMA, Hubble). I will then show how samples of the most luminous objects can constrain the astrophysics at play in early galaxy formation through the observed shape and evolution of the luminosity function. I will end by looking forward to upcoming wide-area surveys from LSST and Euclid, which, when combined with 21cm neutral Hydrogen experiments, will be able to determine the progress and topology of Reionization.