It is demonstrated how a novel X-ray diffraction method can provide information on the structural dynamics of the individual grains inside a Bi-222-3/Ag tape. A microfocused beam of 80 keV X-rays provides both the necessary spatial resolution and penetration power for in situ studies. In a feasibility study at the European Synchrotron Radiation Facility a green mono-filamentary tape is annealed in air for 12 h at 838.5 degreesC. The Bi-2212 to Bi-2223 transformation is found to be a dynamical process during which individual Bi-2212 grains form, dissociate and "recrystallise" at different times throughout the annealing. The typical reaction time is 1 It. The potential of the method for classifying grains according to orientation, volume and stoichiometry is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.