On July 13,2019 at 14:41 CEST the X-ay space observatory Spectrum-Roentgen-Gamma (SRG) was successfully launched from the Baikonur cosmodrome. It carries two X-ray telescopes, ART-XC, which was developed under the lead of the space research institute IKI, Moscow and eROSITA, which was developed and built by a consortium of German institutes under the direction of the Max-Planck-Institute for Extraterrestrial Physics (MPE) and with support from the German Space Agency at DLR. \r\n\r\nMeanwhile (November 2019) SRG has reached the halo orbit around L2, 1,5 million kilometers from Earth. eROSITA is in its calibration and performance verification phase, and this early data confirm the excellent performance of the instrument. Starting in December, eROSITA will carry out eight complete X-ray surveys over the next four years, creating the first complete sky map in the medium X-ray range. At lower energies it will approximately 25 times more sensitive than the previous ROSAT mission. In addition it has much better spectroscopic capabilities.\r\n \r\nThe main scientific goal of eROSITA is to map the large scale structure of the universe and to find out how these structures grow in the course of cosmic time. Clusters of Galaxies which track this structure are filled with millions of degrees of hot plasma and can be detected directly by an X-ray telescope. eROSITA is designed to detect 100.000 clusters of galaxies to reconstruct also the history of their growth. This, in turn, will tell us about the amount and perhaps the nature of the enigmatic dark energy and dark matter.