Controlling　phase　transition　in　functional　materials　at　nano　scale　is　not　only　of　broad　scientific　interest　but　also　important　for　practical　applications　in　the　fields　of　renewable　energy,　information　storage,　transducer,　sensor,　and　so　forth.　As　a　model　functional　material,　vanadium　dioxide　(VO2)　has　its　metal　insulator　transition　(MIT)　usually　at　a　sharp　temperature　around　68　degrees　C.　Here,　we　report　a　focused　electron　beam　can　directly　lower　down　the　transition　temperature　of　a　nanoarea　to　room　temperature　without　prepatterning　the　VO2.　This　novel　process　is　called　radiolysis-assisted　MIT　(R-MIT).　The　electron　beam　irradiation　fabricates　a　unique　gradual　MIT　zone　to　several　times　of　the　beam　size　in　which　the　temperature-dependent　phase　transition　is　achieved　in　an　extended　temperature　range.　The　gradual　transformation　zone　offers　to　precisely　control　the　ratio　of　metal/insulator　phases.　This　direct　electron　writing　technique　can　open　up　an　opportunity　to　precisely　engineer　nanodomains　of　diversified　electronic　properties　in　functional　material-based　devices.