In a collaboration between Stanford and Lawrence Berkeley Lab, researchers have put forward a proposal to use magnetic mirroring to implement a multi-pass transmission electron microscope. The claim is that it will become possible to reduce shot noise in the image or, alternatively, to reduce specimen damage at constant shot noise. So far, this is a simulation study, but the authors plan to build a demonstration system. [Ref. 1]
Interestingly, a group in Madrid has posted a nice overview of outstanding problems in cryo-EM. Surprisingly, they claim that simple issues like magnification calibration and focus determination are still quite challenging. [Ref. 2] Certainly, having higher S/N ratio would be advantageous.