Abstract: A method for making a 3D photonic crystal includes: (a) preparing a liquid mixture including a solvent component, a particulate material suspended in the solvent component, and a filler suspended or dissolved in the solvent component, with the proviso that, when the filler is suspended in the solvent component, the filler has an average size smaller than an average size of the particulate material; (b) allowing a 3D photonic structure to grow from the liquid mixture; and (c) removing liquid from the 3D photonic structure. The method can further include (d) removing the particulate material from the 3D photonic structure after the step (c). In this case, the particulate material and the filler are made of different materials.