Abstract : To take advantage of nanostructures beyond their large surface area for light‐activated gas sensing, in article number 2001883, Seokwoo Jeon, Young‐Seok Shim, Ho Won Jang, and co‐workers introduce a new class of UV‐activated sensing of rationally designed highly periodic 3D TiO2 . The 3D TiO2 facilitates 55 times enhanced light absorption and ultra‐sensitive NO2 sensing properties with a detection limit of ∼200 ppt at room temperature.