The INTEGRAL satellite, which studies the Universe in the hard X-ray and soft Gamma-ray domain, has been operational for 5 years now. The X-ray telescopes, which use the coded mask technique, provide unprecedented spectral and imaging resolution. This led to a number of discoveries, such as the distribution of diffuse emission in the Galaxy, the discovery of highly absorbed sources and fast X-ray transients in the Galactic Plane, localization of ~50 Gamma-ray bursts, and the resolution of the cosmic X-ray background around its peak at 30 keV. About 300 previously known X-ray sources have been detected and in addition more than 200 new sources have been discovered. INTEGRAL provides spectra starting at 3 keV and ranging up to several hundred keV. This article gives a brief overview about the major discoveries of INTEGRAL.