Hybrid organic-inorganic halide perovskites have attracted paramount interest due to their adjustable band gap, solution processibility for solar cells and excellent optoelectronic properties, and its solar cells power conversion efficiencies have reached higher than 25%. In this brief review, we provide a brief overview of phase transformation and conversion for different kinds of hybrid perovskites as revealed through in-situ grazing incidence wide-angle X-ray scattering（GIWAXS） technique. These experiments were performed in conditions closely mimicking thin film processing and conditions used for thin film solar cell device fabrication, therefore have provided critical information about the mechanism of the phase transformation, its onset, kinetics, as well as the emergence and disappearance of various phases along hybrid perovskite film formation. These measurements capture the overall solidification and conversion process of hybrid perovskite inks into solid films, all of which deeply affect the thin film microstructure and morphology. This paper may be helpful for designing and fabricating high performance perovskite optoelectronics.