The eROSITA All-Sky Survey and its spectroscopic follow-up

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian/German Spektrum-Roentgen-Gamma (SRG) mission which is current scheduled for launch in 2016. In the soft band (0.5-2 keV), the deep All-sky survey will be 30 times more sensitive than the previous ROSAT All-sky survey, while the first ever true all-sky survey will be mapped in the hard band (2-8 keV).The design driving science is the detection of large samples of galaxy clusters to redshifts z > 1, in order to study the large scale structure in the Universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of around 3 million active galactic nuclei, which is bound to revolutionize our view of the evolution of supermassive black holes and their impact on the process of structure formation in the Universe.I will review the main characteristics of eROSITA All-sky survey, with an eye also on the planned spectroscopic follow-up of the sources with SDSS-IV/SPIDERS and ESO/4MOST.