Falling sphere viscosity measurement was developed using white X-ray radiography with high-speed camera (>1000 frame/second). The high-speed white x-ray radiography setup enables us to investigate viscosity of a wide range of materials including very low viscos liquids (around 1 mPa s or less). Figure 1 shows an example of X-ray radiography images of falling of WC sphere in liquid sulfur in PE cell at high pressure recorded with 5000 frames/second and 0.2 ms exposure time.   In addition, the viscosity measurement can be combined with liquid structure measurement to investigate in situ correlation between structure and viscosity of liquids at high pressures.