Three new ways are proposed to "structure" bubbling gas-solid fluidized beds, i.e. to bring order into their chaotic hydrodynamics. Just like for fixed bed reactors, the rational structuring of fluidized beds, a novel concept, is interesting from the point of view of process intensification, to facilitate scale-up and control, and to improve performance. Applying an AC electric field, reduces the average bubble size by manipulating interparticle forces. Introducing part of the gas via a fractal injector, immersed into the bed, homogenizes the bed contents, considerably improves gas-solid contact, and simplifies scale-up. Oscillating the gas flow transforms chaotic bubble motion into remarkably regularly ordered patterns of rising bubbles. (C) 2003 Elsevier B.V. All rights reserved.