Despite　their　potential　in　various　fields　such　as　soft　robots,　drug　delivery　and　biomedical　engineering,　magnetic　hydrogels　have　always　been　limited　by　their　poor　mechanical　properties.　Here　a　universal　soaking　strategy　has　been　presented　to　synthesize　tough　magnetic　nanocomposite　(NC)　hydrogels.　We　can　simultaneously　solve　two　common　issues　for　magnetic　hydrogels:　the　poor　mechanical　properties　and　poor　distribution　of　magnetic　particles.　The　toughness　of　the　magnetic　NC　hydrogel　achieves　approximately　11　000　J　m(-2).　The　outstanding　properties　of　tough　magnetic　hydrogels　will　enable　myriad　applications.　Here　we　demonstrate　a　new　application　for　remotely　triggered　shape　morphing.　Heterogeneous　structures　based　on　magnetic　hydrogels　are　shown　to　evolve　into　bio-inspired　three-dimensional　(3D)　shapes　(lotus　flowers)　from　2D-structured　sheets.　The　self-folding　of　the　structure　is　controlled　by　the　magnetothermal　effect　in　an　alternating　magnetic　field.　The　capability　to　control　the　shape　morphing　of　a　multi-material　system　by　a　magnetic　field　may　emerge　as　a　new　general　strategy　for　programming　complex　soft　structures.