In conventional RESS processes, tuning of the pressure and temperature enables the particle size to be manipulated [7], [8], [9], [10], [11] and [12], although subsequent growth and aggregation make it difficult to maintain the desired size. In the process described here, the conditions within the fluidized bed can also be used to tune the particle size. In the near/supersonic free jet, the pressure, temperature and supersaturation change very rapidly along the expansion path, so that nucleation can occur within a distance of less than a millimetre from the nozzle tip or even within the nozzle itself [14].