The　inherent　material　imperfections　of　solid　core　optical　fiber,　for　example,　Kerr　nonlinearity,　chromatic　dispersion,　Rayleigh　scattering　and　photodarkening,　set　fundamental　limitations　for　further　improving　the　performances　of　fiber-based　systems.　Hollow-core　fiber　(HCF)　allows　the　light　to　be　guided　in　an　air　core　with　many　unprecedented　characteristics,　overcoming　almost　all　the　shortcomings　arising　from　bulk　material.　The　exploitation　of　HCF　could　revolutionize　the　research　fields　ranging　from　ultra-intense　pulse　delivery,　single-cycle　pulse　generation,　nonlinear　optics,　low　latency　optical　communication,　UV　light　sources,　mid-IR　gas　lasers　to　biochemical　sensing,　quantum　optics　and　mid-IR　to　Terahertz　waveguides.　Therefore,　the　investigations　into　the　guidance　mechanism　and　the　ultimate　limit　of　HCF　have　become　a　hot　research　topic.　In　the　past　two　decades,　scientists　and　engineers　have　fabricated　two　types　of　high-performance　HCFs　with　loss　figures　of　1.7　dB/km　and　7.7　dB/km　for　hollow-core　photonic　bandgap　fiber　(HC-PBGF)　and　hollow-core　anti-resonant　fiber　(HC-ARF)　respectively.　In　comparison　with　the　twenty-years-old　HC-PBGF　technology,　the　HC-ARF　that　recently　appeared　outperforms　the　former　in　terms　of　broadband　transmission　and　high　laser　damage　threshold　together　with　a　quickly-improved　loss　figure,　providing　an　ideal　platform　for　many　more　challenging　applications.　While　the　guidance　mechanism　and　fabrication　technique　in　HC-PBGF　have　been　well　recognized,　the　HC-ARF　still　has　a　lot　of　room　for　improvement.　At　the　birth　of　the　first　generation　of　broadband　HC-ARF,　the　guidance　mechanism　was　unclear,　the　fiber　design　was　far　from　perfect,　the　fabrication　was　immature,　and　the　optical　properties　were　not　optimized.　In　the　past　five　years,　we　have　developed　an　intuitive　and　semi-analytical　model　for　the　confinement　loss　of　HC-ARF　and　managed　to　fabricate　high-performance　nodeless　HC-ARF.　We　further　employ　our　theoretical　model　and　fabrication　technique　to　well　control　and　design　other　interesting　properties,　such　as　polarization　maintenance　and　bending　loss　in　HC-ARF.　For　a　long　time,　the　anti-resonant　theory　of　light　guidance　has　been　regarded　as　being　qualitative,　and　the　leaky-mode-based　HC-ARF　have　been　considered　to　have　worse　performances　than　the　guided-mode-based　HC-PBGF.　Our　investigations　in　theory　and　experiment　negative　these　prejudices,　thus　paving　the　way　for　the　booming　development　of　HC-ARF　technologies　in　the　near　future.