Our group is focusing on controlling the perovskite growth on different substrates by using low temperature methods. Recently Wenxin Mao uses low temperature solution based method to synthesize a one dimensional (MA)[PbBr3]·DMF, and demonstrates its facile transformation into monocrystalline MAPbBr3 microplatelets. The MAPbBr3 microplatelets were tailored into waveguide based photonic devices, of which an ultra-low propagation loss of 0.04 dBmm-1 for a propagation distance of 100 mm was demonstrated. This paper is published on Angewandte Chemie International Edition as a front cover issue (Angew. Chem. Int. Ed. 2017, 56, 12486 –12491).