In　the　research　field　of　hollow-core　optical　fiber　(HCF),　one　type　of　fiber　geometry　with　a　leaky　mode　nature　has　unexpectedly　taken　center　stage　over　the　last　couple　of　years:　the　so-called　hollow-core　anti-resonant　fiber　(ARF).　The　guidance　mechanism　of　this　ARF　has　been　elucidated　explicitly,　the　optical　performance　of　the　fiber　has　improved　significantly,　and　the　range　of　potential　fiber　application　areas　has　expanded　steadily.　This　paper　will　review　our　continuous　efforts　to　understand,　design,　and　fabricate　this　hollow-core　ARF　with　the　aim　of　lower　loss　and　wider　bandwidth.　We　also　explore　the　possibility　of　using　an　advanced　form　of　ARF　in　communications　applications.　In　the　long　journey　of　looking　for　optical　fibers　that　provide　better　performance　than　conventional　solid-core　glass　fibers,　exploitation　of　the　hidden　potential　of　artificial　photonic　micro-structures　will　continue　to　advance.