Electron tomography provides a 3-D reconstruction derived from a series of projection images recorded as the specimen is tilted in the microscope.[1] Despite the challenges of low contrast and sensitivity to beam-induced specimen damage, electron tomography can be applied to frozenhydrated biological material. This avoids the necessity for chemical fixation, dehydration, and straining, and thus allows study of the specimen in a “near-native” state. A variety of specimens have been studied in aqueous suspension by electron tomography of thin films of vitreous ice prepared by rapid plunging into a cryogen. These include microorganisms and molecules [2], mitochondria [3,4], and the skeletal muscle triad junction.[5] We have succeeded in extending this 3-D imaging technique to frozen-hydrated tissue sections, which makes it possible to study a wide range of “native” sub-cellular structures in situ.