In a TEM, electromagnetic lenses have been shown not to interfere noticeably with observations of reciprocity, provided that elastic scattering processes dominate in the sample and the sample is not strongly magnetic. Careful application of the reciprocity theorem in cases where it is valid give a TEM user considerable flexibility in taking and interpreting images and electron diffraction patterns. Reciprocity may also be used to understand scanning transmission electron microscopy (STEM) in the familiar context of TEM, and to obtain and interpret images using STEM.