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　H　2　,　CO,　and　O　2　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　MnO　2　is　coated　on　the　microporous　Ni　wire　(MPNW)　to　form　a　supercapacitor　electrode.　The　MnO　2　/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