Controlled synthesis of transition-metal hydroxides and oxides with earth-abundant elements have attracted significant interest because of their wide applications, for example as battery electrode materials or electrocatalysts for fuel generation. Here, we report the tuning of the structure of transition-metal hydroxides and oxides by controlling chemical reactions using an unfocused laser to irradiate the precursor solution. A Nd:YAG laser with wavelengths of 532 nm or 1064 nm was used. The Ni2+ , Mn2+ , and Co2+ ion-containing aqueous solution undergoes photo-induced reactions and produces hollow metal-oxide nanospheres (Ni0.18 Mn0.45 Co0.37 Ox ) or core-shell metal hydroxide nanoflowers ([Ni0.15 Mn0.15 Co0.7 (OH)2 ](NO3 )0.2 ⋅H2 O), depending on the laser wavelengths. We propose two reaction pathways, either by photo-induced redox reaction or hydrolysis reaction, which are responsible for the formation of distinct nanostructures. The study of photon-induced materials growth shines light on the rational design of complex nanostructures with advanced functionalities.