Technology is currently poised at the boundary of three grand challenges in structural biology:

1. High-resolution imaging of isolated biomolecules of varying sizes, enabling the determination of atomic models.

2. Tomography at sub-nanometer resolution with a wide field of view, showing the structural arrangement and positive identification of chemical components in a cellular environment.

3. Biomolecular dynamics at nm-s resolutions, enabling visualization of biomolecular function: complex assembly, signal transduction, folding, etc.

Recent developments in cryoEM instruments (direct detectors) and x-ray sources (XFELs) have brought these goals tantalizingly close. One promising avenue to addressing all three goals is to advance the electron source technology behind electron microscopy, improving the performance of electron microscopes to encompass one or more of the above goals.

In this paper, we consider the construction of a pulsed MeV instrument to further these goals, and conclude:

1. Single-shot (including diffract-before-destroy) imaging modes of atomic structure are likely impossible with electrons. Current technology is very far from making this achievable, and the requirements are close to the limits dictated by quantum mechanics for relativistic electron beams.

2. It is not clear that MeV beams provide a clear advantage to image formation via improved damage, detectors, sample thickness, or jitter removal.

3. MeV beams can provide a modest improvement to resolution via improved contrast transfer,

4. An emphasis should be placed on increasing {more}... Show Partial Abstract