Ultra-high-speed injection molding, in which the cavity filling time may generally be less than 30ms, is widely utilized especially for ultra-thin-wall molding products. The ultra-high-speed in-mold phenomena exemplified by this technology, are quite difficult to analyze with existing visualization and experimental technologies. Under such circumstances, new methods and technologies are expected to be developed for solving the above problems; e.g., visualization method with higher time/special resolution, and mold structures with higher pressure endurance, etc. This article introduces the overall advancement of visualization technologies applied inside the injection mold, and their potentialities through application results of new visualization and measuring technologies, which our research group has successfully developed in the past seven years, focusing on the experimental analysis of ultra-high-speed injection molding phenomena.