This document summarizes research on using optical coherence tomography (OCT) to characterize coronary plaques. OCT uses near-infrared light to generate high-resolution cross-sectional images of tissue microstructure. Researchers studied 357 arterial segments ex vivo using OCT and validated plaque types (fibrous, calcific, lipid-rich) against histology with high accuracy. A pilot clinical study of 10 patients found OCT feasible and safe for in vivo coronary imaging before and after percutaneous coronary intervention, identifying a variety of plaque types and stent appositions. While blood obstruction and motion artifacts posed challenges, the results support further evaluation of OCT as a potential "optical biopsy" tool.