This paper reports some of the results obtained from a series of experimental campaigns, carried out over several years, aimed at visualizing the flow patterns occurring inside large-scale fluidized beds by applying an X-ray imaging technique. For over 12 years, BP has been developing and applying an X-ray imaging technique as part of its research and development programmes for both Oil and Chemicals technologies. This paper illustrates how BP has used the X-ray technique to identify some important process issues, in particular how factors like process designs and operating conditions like temperature, pressure and gas velocity influence the fluidization behaviour. Examples taken from BP Chemicals Gas Phase High Productivity (INNOVENE) technology are discussed, and the synergies with Fluid Catalytic Cracking (FCC) spray nozzle technology are highlighted. Within an FCC unit. this technique has been extensively applied to the catalyst and gas interactions within the regenerator and stripper vessels, and to air, steam and feed nozzle evaluations.