Schematic diagram of the mechanism for QPEs. A hydrogen-deficient post-AGB star with He envelope orbits around an SMBH on an eccentric orbit. When the star approaches periapsis, it just fills its Roche lobe. The He envelope with low density ends up partially tidally stripped by the SMBH, while the compact core survives the encounter. Finally, the stripped material falls back to the SMBH, resulting in QPEs.