Optical coherence tomography (OCT) is an emerging biomedical imaging technology that enables micronâ€‘scale, crossâ€‘sectional, and three-dimensional (3D) imaging of biological tissues non-invasively. OCT functions as a type of â€œoptical biopsy,â€ imaging tissue microstructure with resolutions approaching that of standard histopathology by microscopy, but without the need to remove and process tissue specimens. OCT is analogous to ultrasound imaging, except that light instead of sound is used in OCT to provide 10â€“100 times better resolution compared to ultrasound. To date, OCT has been used in a wide range of clinical applications in humans, including ophthalmology, cardiology, endoscopy, oncology, dermatology, and dentistry. Our group developed a space-division multiplexing OCT (SDM-OCT) technology that achieved over 20-fold speed improvement compared to current state-of-the-art commercial OCT systems. The key of the SDM-OCT technology is to create multiple imaging beams to illuminate the sample simultaneously, while having different optical delays for each beam. Since each optical beam was optically delayed, signal from different sample locations was presented at different frequency range, enabling parallel OCT imaging in order to achieve significant improvement in imaging speed.