This paper aims to give an overview on the recent progress of controlled colloidal assembly as a unique experimental modeling system to study the general crystallization mechanism, i.e., the kinetics of nucleation, growth, and defects formation, and as a template for photonic crystals engineering. Such a system allows us not only to visualize some atomic details of the nucleation and surface process of crystallization, but also to treat quantitatively the previous models to an extent that has never been achieved before by other approaches. As such, the kinetic process of nucleation was quantitatively examined at the single particle level for the first time, allowing the identification of the deviations from the classical theories. The application of the electrically controlled colloidal crystallization to the modeling of the kinetics of some important processes of crystallization, i.e., multistep crystallization, supersaturation-driven structural mismatch nucleation, defect creation and migration kinetics, surface roughening, etc., has brought our knowledge to a new phase. Apart from the fundamental aspects, the controlled colloidal crystallization has attracted significant attention in many applications. In this regard, the application of colloidal crystallization to the fabrication of photonic crystals and the biomimicking of natural structure colors will be examined.