First Results from eROSITA Observations of Galaxy Clusters Detected in the eFEDS Field

Galaxy clusters trace the highest peaks in the cosmic density field and offer an independent and powerful probe of the growth of structure and their abundance is strongly dependent on the underlying cosmology. The availability of the new catalogues with 100000 clusters, eROSITA All Sky Survey in the X-ray band will put us on the verge of a breakthrough in precision cosmological measurements. I will present the first results on groups and clusters of galaxies from the eROSITA Final Equatorial Survey (eFEDS) performed during the Performance Verification phase and summarise the plans for the All-Sky Survey.