Optical coherence tomography (OCT)Optical coherence tomography (OCT) is a noninvasive imaging technology that provides high-resolution, cross-sectional images of biological tissues and organoids. Since its inception in 1990, OCT has become the gold standard for diagnosing various ophthalmic conditions, such as age-related macular degeneration and glaucoma. Based on low-coherence interferometry, OCT offers superior resolution compared to conventional ultrasound imaging while maintaining a penetration depth suitable for many applications. This method is particularly advantageous in clinical settings, allowing for real-time imaging without the need for tissue removal or dyes, thus preserving the integrity of the sample. Recent advancements have extended the utility of OCT to imaging 3D cell cultures, including organoids and spheroids, which are crucial for drug testing and cancer research. The ability to monitor morphological and physiological changes in these complex structures nondestructively is a significant breakthrough in biomedical research. Furthermore, enhancements such as dynamic OCT and Doppler OCT enable researchers to assess cell viability and blood flow dynamics. As a result, OCT continues to bridge the gap between microscopy and traditional imaging techniques, making it an invaluable tool in both clinical diagnostics and scientific research.