Anyone who has recently had an eye examination may have been ushered into a room that contained an optical coherence tomography (OCT) scanner. This technology uses backscattered light to construct cross-section images of the retina, similar to the way sound waves are used to construct an ultrasound image, except at a much higher resolution. Imaging the thickness of the retina can help to reveal various diseases and conditions. Most people who dutifully put their head on the chin rest of the OCT scanner and stare at the red light are unaware of how the technology works. They also may not know that OCT has developed beyond the functionality of the traditional ophthalmology machine they see before their eyes, which was established in the 1990s. The technology has since ventured into realms once dominated by ultrasound and other techniques, to explore not only macular degeneration but also cancer or hindrances to fetal development — and it’s performing these tasks with incredible resolution. Indeed, OCT has come a long way since David Huang and his colleagues published their research on the technique nearly 30 years ago. In its first decade, the technology was considered a breakthrough in studies of the structure of the eye and ocular diseases. With the arrival of the new century, and the evolution of the technology into such areas as OCT angiography and spectral domain OCT, the stage was set for its use in such fields as cardiology, dermatology, and oncology. OCT proved itself invaluable when paired with other optical approaches. It has enhanced traditional endoscopy, and, this year, the technology was successfully paired with autofluorescence imaging in lung biopsies. OCT has even helped inform veterinary medicine, as I detail in this issue’s cover story, due to its ability to resolve tissue of both large and small animals at the micron scale; identify eye conditions in cats, dogs, or stray turtles; delineate cancer tumors for extraction from canines; and determine the joint strength of horses. Other authors in this issue take a deep dive into topics such as using OCT to track health and possible complications in fetal development following a pregnant mother’s use of alcohol and other drugs; and combining the vast number of images generated by the technology with machine learning, allowing for quick scanning and accurate diagnosis. While such techniques have enabled OCT to branch out considerably from its initial uses, it has continued to enhance ophthalmology over the years. In ‘Biopinion,’ a group of authors urges the photonics community to develop new light sources to make VIS-OCT — which is used to examine the vascular network in the eyes — more accessible to researchers in labs and practitioners in clinics, who would most benefit from its high-resolution capabilities. Coming early in 2021, readers will be able to experience virtual lessons in OCT by participating in several sessions of the Biomedical Imaging track of the Photonics Spectra Conference, sponsored by our sister magazine. Learn more about the conference here, and register for free at www.PhotonicsSpectraConference.com. Enjoy the issue!