Platinum　nanoparticles　(NPs)　supported　by　titania　exhibit　a　strong　metal-support　interaction　(SMSI)[1]　that　can　induce　overlayer　formation　and　encapsulation　of　the　NP＇s　with　a　thin　layer　of　support　material.　This　encapsulation　modifies　the　catalyst＇s　properties,　such　as　increasing　its　chemoselectivity[2]　and　stabilizing　it　against　sintering.[3]　Encapsulation　is　typically　induced　during　high-temperature　reductive　activation　and　can　be　reversed　through　oxidative　treatments.[1]　However,　recent　findings　indicate　that　the　overlayer　can　be　stable　in　oxygen.[4,　5]　Using　in　situ　transmission　electron　microscopy,　we　investigated　how　the　overlayer　changes　with　varying　conditions.　We　found　that　exposure　to　oxygen　below　400　°C　caused　disorder　and　removal　of　the　overlayer　upon　subsequent　hydrogen　treatment.　In　contrast,　elevating　the　temperature　to　900　°C　while　maintaining　the　oxygen　atmosphere　preserved　the　overlayer,　preventing　platinum　evaporation　when　exposed　to　oxygen.　Our　findings　demonstrate　how　different　treatments　can　influence　the　stability　of　nanoparticles　with　or　without　titania　overlayers.　expanding　the　concept　of　SMSI　and　enabling　noble　metal　catalysts　to　operate　in　harsh　environments　without　evaporation　associated　losses　during　burn-off　cycling.　©　2023　The　Authors.　Angewandte　Chemie　International　Edition　published　by　Wiley-VCH　GmbH.