Electromagnetic Radiation Shielding In article number 2401264, Quyen Vu Thi, Daewon Sohn, Vinh Xuan Truong, and co-workers discover that poly (acrylic acid) hydrogels, when combined with multi-walled carbon nanotubes, can form robustly porous composite hydrogels with excellent electromagnetic interference (EMI) shielding. The outstanding shielding efficiency, (> 99.99%) under extremely acidic environments, paves toward applications of 3D hierarchical network materials for EMI applications in both land and aqueous environments.