Abstract: Metals and their alloys are an important type of structural and functional material and have been widely used in the aerospace, automobile, shipbuilding and other industries.The macro-properties of metallic alloys actually depend on their microstructures.The evolution of their microstructures generally involves a dynamic process of crystal growth on the scale of micrometers.The crystal growth of these alloys is still a puzzle to us due to their opacity.Conventional metallography techniques are limited by the high temperature of the phase changes so it is not possible to perform in situ observation of the evolving crystal morphology.The in situ visualization of the crystal growth has now become possible with the application of synchrotron radiation imaging techniques, which are just the right key to unravel the mystery mentioned above.In this paper, the development and current state-of-the-art of in situ crystal growth visualization are reviewed.Some typical application examples are presented, and promising applications in materials science are further expected.