2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/5344We briefly discuss the perspectives of sensitive hard X-ray observations with the large collecting area X-ray telescopes of XEUS.5 pages, 3 colour figures. Proc. workshop "XEUS - studying the evolution of the hot universe", MPE report. LaTeX, xeus.cls includedAstrophysicstext