The last decade has seen unprecedented strides to everimproving resolutions in electron microscopes. To focus the electrons, these microscopes use round electromagnetic lenses that, unlike glass lenses in optical microscopes, have a positive spherical aberration [1]. Because of this electrons traveling at larger angles away from the incident beam direction are focused more strongly than those traveling at smaller angles, blurring the image. While the wavelength of the electrons used is very small, typically in the range 0.02 − 0.037 angstroms, for many years it was impossible to come close to the theoretical wavelength-limited resolution because of the finite spherical aberration. A commonly used analogy is that taking images with imperfect electron microscope lenses is like trying to see through glass milk bottles. It has been known for many years that the way to create negative spherical aberration magnetic lenses is to break the symmetry and use multipole lenses [1]; with round lenses the magnetic field lines are largely parallel to the electron beam direction, whereas in multipole lenses they are perpendicular to it. However, this involves controlling a very large number of different lens elements at the same time, which proved difficult until computer control was introduced (e.g., Refs. [2, 3]). Not too long after this, designs to correct the next large problem, chromatic aberration (focal length dependent on wavelength) appeared and were quickly implemented in commercial machines [4]. It looked like electron microscopes were on the path to ever-increasing resolution, with no foreseeable barriers to ever-better performance. Alas, it appears this was too optimistic. In Physical Review Letters, Stephan Uhlemann and colleagues at Corrected Electron Optical Systems GmbH (CEOS), Germany, report an unexpected limit to resolution [5], namely, magnetic noise caused by thermal activation of currents or spins in the metal components. Due to the longer optical path that they travel in aberration-corrected instruments, the electrons are sensitive to very small magnetic fields, which the authors estimate to be of the order of 0.1 nanotesla, about a hundred thousand times smaller than the Earth’s magnetic field. The experiments performed by Stephan Uhlemann and co-workers involved modifying an electron microscope by removing the aberration corrector and replacing it with a tube which could be cooled, and then putting different tubes within it (a stainless steel and a permalloy material were used). They then examined how the resolution depended upon both the inner tube material as well as the temperature, showing a significant improvement at lower temperatures which is consistent with thermal magnetic noise. Any transmission electron microscope contains many metal parts. Most of these parts are structural but others carry current for lenses, are involved in transmission of magnetic fields, or are part of apertures used to select which parts of the electron beam are involved in the final image or spectra. Often these are inhomogeneous alloys containing precipitates, dislocations, grain boundaries, and other phases chosen to improve mechanical and electrical performance or simply cost. At any given instance of time there can be local fluctuations in electrical currents/spins (what is called Johnson-Nyquist noise [6, 7]), as illustrated in Fig. 1, which lead to fluctuating magnetic fields in sensitive magnetic devices such as SQUIDS. While the time-averaged effect of these fields is small, the swift electrons in the microscope are traveling at about half the speed of light and so can be deflected by the instantaneous magnetic fields. Time averaged over the many electrons that make up the final image (typically 103–105 are detected in any single pixel of a CCD camera), this reduces the coherence of the electron beam and consequently the resolution. The authors estimate that the resulting resolution limit is in the range 0.5–0.8 A, which is consistent with the best that has been achieved to date. Of course, improving the resolution to (for instance)