The article introduces a novel approach to improve the tiling process in transmission electron microscopy (TEM) by using a square electron beam. Traditional TEMs typically use round beam profiles, which can lead to imperfect tiling or uneven exposures, especially for dose-sensitive samples like vitrified biological materials. The authors demonstrate that a square electron beam can be retrofitted into existing microscopes to achieve nearly perfect tiling and deliver cryo-electron microscopy imaging with high resolution. The key innovation is the use of a square aperture in the C2 lens of a 3-condenser system, which allows for the creation of a square beam profile. This setup ensures that the entire sample area exposed to the beam is imaged, minimizing overlap and maximizing the field of view. The authors show that this method significantly improves data collection efficiency, particularly in single-particle analysis, and achieves comparable resolution to conventional setups. The article also discusses the technical details of implementing the square beam, including the adjustments needed to align the beam with the sensor and the calibration required after changes in the P2 lens. The authors provide examples of successful imaging using the square beam, including montage tomography and single-particle reconstructions, demonstrating the effectiveness of the approach. Overall, the introduction of a square electron beam offers a practical solution to the limitations of round beams in TEM, particularly for high-resolution imaging of dose-sensitive samples.The article introduces a novel approach to improve the tiling process in transmission electron microscopy (TEM) by using a square electron beam. Traditional TEMs typically use round beam profiles, which can lead to imperfect tiling or uneven exposures, especially for dose-sensitive samples like vitrified biological materials. The authors demonstrate that a square electron beam can be retrofitted into existing microscopes to achieve nearly perfect tiling and deliver cryo-electron microscopy imaging with high resolution. The key innovation is the use of a square aperture in the C2 lens of a 3-condenser system, which allows for the creation of a square beam profile. This setup ensures that the entire sample area exposed to the beam is imaged, minimizing overlap and maximizing the field of view. The authors show that this method significantly improves data collection efficiency, particularly in single-particle analysis, and achieves comparable resolution to conventional setups. The article also discusses the technical details of implementing the square beam, including the adjustments needed to align the beam with the sensor and the calibration required after changes in the P2 lens. The authors provide examples of successful imaging using the square beam, including montage tomography and single-particle reconstructions, demonstrating the effectiveness of the approach. Overall, the introduction of a square electron beam offers a practical solution to the limitations of round beams in TEM, particularly for high-resolution imaging of dose-sensitive samples.