In the era of precision cosmology and redshift-deepening observation, probing the astrophysical objects in their infancy is getting ever more important. Difficulty of drop-out techniques to probe high-redshift stellar objects at z>~7 can be compensated by high-sensitivity radio telescopes, strating from several precursors (LOFAR, MWA, PAPER, 21CMA, etc.) but ending ultimately by the Square Kilometre Array (SKA) aiming to probe the Universe down to z~28. Cosmic microwave background (CMB) also bears important information on this high-redshift epoch, in terms of anisotropy in temperature and polarization. I will brief on recent theoretical developments in the astrophysics and cosmology at such high-redshift epoch, and describe how radio astronomy can perform both of these disciplines, with biased focus on SKA.