Mirror-image inversion in commonly used compound microscopes

Optical microscopes are essential tools for magnifying and analyzing a wide range of samples and are expected to faithfully preserve the original object in all its dimensions. However, while examining cerebral structures with left-right asymmetry, we discovered that the image of the object can be unintentionally mirror-inverted, depending on the microscope setup. This inversion mostly goes unnoticed, leading to incorrectly oriented images, loss of image integrity, and potential misinterpretation. We detail the optical origins of this issue and offer a practical guide to support accurate sample imaging, while urging manufacturers to explicitly communicate how their systems affect image orientation.