  The question of the X-ray background has been largely settled over the last
10 years using the ROSAT satellite. About 70-80 % of the soft X-ray background
was resolved into discrete sources, which are mainly X-ray and optically
unobscured AGNs (Quasars, Sy1). Furthermore we found already several obscured
AGNs in deep ROSAT surveys, which are predicted by the population synthesis
models for the X-ray background, based on the unified AGN schemes. However,
deep X-ray surveys using Chandra} and XMM-Newton allow to test the reliability
of these models, which seem to be still far from unique. Recent observations
with Chandra and XMM-Newton have resolved most of the hard X-ray background
into discrete sources. The first deep XMM-Newton survey was performed in the
Lockman Hole region, one of the sky areas best studied over a wide wavelength
range. About 100 ksec good exposure time have been accumulated with the EPIC
camera during the performance verification phase. We reach a limiting flux of
0.31, 1.4 and 2.4 x 10E-15 erg/cm2/s in the 0.5-2, 2-10 and 5-10 keV energy
bands. A significant number of X-ray sources show hard, probably intrinsically
absorbed X-ray spectra. We discuss the X-ray, optical and infrared properties
of these sources in comparison with the predictions of the recent X-ray
background models.
