Cellular　metals　with　the　large　surface/volume　ratios　and　excellent　electrical　conductivity　are　widely　applicable　and　have　thus　been　studied　extensively.　It　is　highly　desirable　to　develop　a　facile　and　cost-effective　process　for　fabrication　of　porous　metallic　structures,　and　yet　more　so　for　micro/nanoporous　structures.　A　direct-flame　strategy　is　developed　for　in　situ　fabrication　of　micron-scale　cellular　architecture　on　a　Ni　metal　precursor.　The　flame　provides　the　required　heat　and　also　serves　as　a　fuel　reformer,　which　provides　a　gas　mixture　of　H2,　CO,　and　O2　for　redox　treatment　of　metallic　Ni.　The　redox　processes　at　elevated　temperatures　allow　fast　reconstruction　of　the　metal,　leading　to　a　cellular　structure　on　Ni　wire.　This　process　is　simple　and　clean　and　avoids　the　use　of　sacrificial　materials　or　templates.　Furthermore,　nanocrystalline　MnO2　is　coated　on　the　microporous　Ni　wire　(MPNW)　to　form　a　supercapacitor　electrode.　The　MnO2/MPNW　electrode　and　the　corresponding　fiber-shaped　supercapacitor　exhibit　high　specific　capacitance　and　excellent　cycling　stability.　Moreover,　this　work　provides　a　novel　strategy　for　the　fabrication　of　cellular　metals　and　alloys　for　a　variety　of　applications,　including　catalysis,　energy　storage　and　conversion,　and　chemical　sensing.　©　2018　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim