TiO₂ microscale structures can be prepared from both TiO₂ precursors and TiO₂ nanoparticles (NPs). TiO₂ microscale structures have many advantages compared to TiO₂ NPs powders, such as tunable structure, higher photocatalytic activity, and ease of recovery. For TiO₂ microscale structures, solid spheres and hollow spheres share some similar synthesis methods. However, microscale TiO₂ microscale structures are not easily mass-produced due to the complexity of the synthesis process.