of illumination of the transmitted beam, have been used to obtain atomic resolution images in which the atomic columns of light elements such as oxygen are visible. Differential phase contrast Differential phase contrast (DPC) is an imaging mode which relies on the beam being deflected by electromagnetic fields. In the classical case, the fast electrons in the electron beam is deflected by the Lorentz force, as shown schematically for a magnetic field in the figure to the left. The fast electron with charge −1 passing through an electric field E and a magnetic field B experiences a force F: For a magnetic field, this can be expressed as the amount of beam deflection experienced by the electron, : where is the wavelength of the electron, the Planck constant and is integrated magnetic induction along the trajectory of the electron. This last term reduces to when the electron beam is perpendicular to a sample of thickness with constant in-plane magnetic induction of magnitude . The beam deflection can then be imaged on a segmented or pixelated detector. This can be used to image magnetic and electric fields in materials. While the beam deflection mechanism through the Lorentz force is the most intuitive way of understanding DPC, a quantum mechanical approach is necessary to understand the phase-shift generated by the electromagnetic fields through the Aharonov–Bohm effect. Imaging most ferromagnetic materials require the current in the objective lens of the STEM to be reduced to almost zero. This is due to the sample residing inside the magnetic field of the objective lens, which can be several Tesla, which for most ferromagnetic materials would destroy any magnetic domain structure. However, turning the objective lens almost off drastically increase the amount of aberrations in the STEM probe, leading to an increase in the probe size, and reduction in resolution. By using a probe aberration corrector it is possible to get a resolution of 1 nm. Universal detectors (4D STEM) Recently, detectors have been developed for STEM that can record a complete convergent-beam electron diffraction pattern of all scattered and unscattered electrons at every pixel in a scan of the sample in a large four-dimensional dataset (a 2D diffraction pattern recorded at every 2D probe position). Due to the four-dimensional nature of the datasets, the term "4D STEM" has become a common name for this technique. The 4D datasets generated using the technique can be analyzed