A prime objective of observational astrophysics is to characterize the earliest sources in the first Gyr of the universe, and to peer into the cosmic times when the first stars, black holes and galaxies formed. Although galaxy candidates are now identified up to redshifts of about 10, their faintness typically precludes detailed studies of their nature. Quasars, on the other hand, are the most luminous non-transient sources known and can be studied in detail at the earliest cosmic epochs. The discovery and characterization of a statistically significant sample of quasars at z>6 is crucial to study the epoch of reionization. I will present our progress in building such a statistical sample, which led to tripling the number of these quasars in just the last three years. I will discuss the diverse range of physical properties of this quasar sample as well as our follow-up studies from optical to radio wavelengths, including a new quasar at a record redshift (z=7.5). In particular, recent observations with ALMA revealed the presence of far-infrared companions around the quasars, and provide key constraints on the spatially resolved properties of the quasar host galaxies. Through multi-line ALMA spectroscopy we can also derive first constraints on the physical conditions of the interstellar medium in the quasar hosts. I will also discuss the potential of future JWST observations.