Several examples of the use of high resolution electron microscopy for
the characterization of the microstructure of thin films of YBa2Cu3O7
are given. It is argued that the sample preparation (cross-section pr
eparation) is a very crucial part of the high T(C) superconducting fil
ms as well as the interpretation of the high resolution images. Exampl
es are shown of a Josephson junction on yttria-stabilized ZrO2, YBa2Cu
3O7 on MgO, a La2CuO4-YBa2Cu3O7-La2CuO4 multilayer and the effect of t
he electron beam on the interface of a YBa2Cu3O7-SrTiO3 interface.