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Superclusters comma as the largest cosmic structures comma are important to study the evolution of galaxy clusters and groups comma cosmic baryons openPare.g. comma the warm hot intergalactic mediumclosePar and galaxy evolution. There have been few studies of superclusters in X-rays comma while the X-ray data remain as the key to study the bulk of baryons in superclusters. We select the two richest superclusters from the SDSS-redMaPPer cluster catalog and propose XMM observations to map both of them. They are extreme mass concentrations with the total mass at least several times higher than well-known superclusters like A901-2. The XMM data will be used to map the mass distribution openParalong with our weak-lensing workclosePar comma study merger dynamics and examine the cosmic filaments comma and provide us important insights on superclusters.