  We present a case for developing a millikelvin-temperature transmission
electron microscope (TEM). We start by reviewing known reasons for such
development, then present new possibilities that have been opened up by recent
progress in superconducting quantum circuitry, and finally report on our
ongoing experimental effort. Specifically, we first review possibilities to
observe a quantum mechanically superposed electromagnetic field around a
superconducting qubit. This is followed by a new idea on TEM observation of
microwave photons in an unusual quantum state in a resonator. We then proceed
to review potential applications of these phenomena, which include low dose
electron microscopy beyond the standard quantum limit. Finally, anticipated
engineering challenges, as well as the authors' current ongoing experimental
effort towards building a millikelvin TEM are described. In addition, we
provide a brief introduction to superconducting circuitry in the Appendix for
the interested reader who is not familiar with the subject.
