Quick-freezing methodology has made three major contributions to our ability to relate structure to function: 1. Quick-freezing, especially when followed by freeze-fracture, is suited to study the ultrastructure of unfixed biological material as close to the native state as can possibly be obtained. 2. Physiological events associated with morphological changes at the level of electron microscopic resolution can be stopped at any desired time interval and, thus, analysed against a known time scale and, 3. Microchemical measurements, e.g. of elemental concentrations and their spatial displacements, can be obtained by electron dispersive X-ray microanalysis from freeze-dried frozen sections of quick-frozen biological material. Indeed, it is now possible to investigate, simultaneously, anatomical, physiological and microchemical parameters in a single cell, with a precise time scale thrown in for good measure.In the following I shall describe the techniques that we employ to study the morphology of single intact skeletal muscle fibers of the frog at known time intervals following electrical stimulation. The methodology is the judicious extension, including some modifications, of procedures whose efficacy is mostly uncontroversial and a matter of scientific record.