are oriented in one direction and their assembly and stacking produces the wurtzite hexagonal symmetry. The noncentrosymmetric and anisotropic crystalline structure of wurtzite-like ZnO generates very interesting properties such as piezo-and pyro-electricity: the application of an external stimulus, like mechanical stress or temperature, deforms the tetrahedron structure. This deformation results in a separation between the positive and negative centers of charge, inducing the formation of a dipole moment. [7,8] The polar surface and anisotropic structure of ZnO can be usefully exploited to form different kinds of micro and nanostructures from 0D to 3D, [5] including, but not limited to nanowires, [9][10][11][12] nanotubes, [13,14] nanobelts, [15][16][17][18][19] nanorings, [20] flower-like morphologies, [21][22][23][24][25] multipods, [26,27] tetrapods, [28][29][30] sponge-like structures [31][32][33][34] and so on [29,[35][36][37][38][39] (Figure 1). Therefore, several research efforts have been invested in studying various preparation procedures for ZnO micro and nano-materials. Wet chemical approaches, like sol-gel, hydrothermal growths, electrodeposition and template-assisted routes, [40,41] as well as vapor-phase methods, for example chemical vapour deposition (CVD), physical vapour deposition (PVD) including sputtering and evaporation approaches, [42][43][44] and epitaxial growth methods [45] are among the most used ones. The great advantages of the wet chemical approaches are the high synthesis versatility, low temperature employed and low costs. [9] From the other side, dry methods take advantage of the high quality and excellent control over the level of crystallinity of the synthesized ZnO structures, as well as the absence of contamination and high purity of the final material. [46] The combination of different properties with the ease and high versatile synthesis of ZnO material in different micro and nanostructures offers a huge possibility of potential applications.For example, ZnO is already used as an efficient catalyst in the selective oxidation of involving oxygenates (i.e., alcohols, aldehydes, and carboxylic acids) and in methanol synthesis catalysts. It is also largely applied as protective, anti-corrosion layer in galvanized steel products, [49][50][51] as well as in paints and sunscreens as an UV absorber. Its biocompatibility makes this material suitable, in the form of microparticles, for paste formulations in cosmetic applications.The combination of the piezoelectric with the semiconducting properties of ZnO is found to result into new exciting physical properties, [52][53][54] and it has recently opened the research field to energy harvesting application. ZnO nanomaterials can be thus used as nanogenerators, able to convert the mechanical deformation from the surrounding environment into electrical Zinc Oxide (ZnO) nanostructures represent promising substrate materials for numerous applications, ranging from new generation solar cells, to bio-and chemical sensors. This interest is due ...