"This project is aimed at better understanding the re-ionisation of the Universe and the star-formation history over cosmic time. Gamma-ray bursts (GRBs), the brightest explosions in the Universe, offer a direct means of answering these questions via observations of their afterglows and host galaxies. The Swift satellite and its ability to rapidly and accurately locate 100 GRBs/year now makes this feasible. This will be complemented with wide-ranging follow-up programmes on numerous telescopes, e.g. the Very Large Telescope (including a new groundbreaking instrument, X-shooter) and the Hubble Space Telescope. The main objectives are: (1) Determine the ionisation history of the Universe and characterise the sources that drive it. The luminosity of GRB afterglows offers a unique opportunity to measure the evolution of the intergalactic medium out to very high redshift. High-redshift GRBs (z > 6) will be discovered via rapid optical/NIR observations, thus enabling subsequent prompt spectroscopy to obtain both the redshift and neutral hydrogen fraction. Deep, late-time observations will allow the identification of star-forming proto-galaxies in the early Universe, the very sources leading to re-ionisation. (2) Compile a comprehensive, uniformly selected sample of GRBs with measured redshifts. This is crucial in order to investigate their energetics and their possible application as ""standard candles"". It is also prerequisite to using the GRB redshift distribution to characterise the star-formation history of the Universe. (3) Understand the nature and evolution of galaxies at high redshift via observations of GRB hosts and their place within the zoo of high-redshift galaxies. Selection by GRBs rather than via galaxy properties allows us to probe the very faint end of the star-forming galaxy luminosity function."