Spatially resolved laser micro‐annealing (process shown on inside front cover) has been used to drive an amorphous to nanocrystalline phase transition in Si inverted colloidal photonic crystals to create micrometer‐sized refractive index patterns (observed as the yellow color in the Figure). This provides a simple means of tailoring the optical properties of Si photonic crystals, and has applications in photonic crystal miniaturized optical components, devices, and circuits.