Intravascular ultrasound represents the most established, well-validated, and widely used intracoronary imaging technology worldwide and was introduced approximately 25 years ago. Intravascular ultrasound enables the visualization of key anatomical structures of the coronary artery and saphenous or arterial grafts including the lumen, external elastic membrane, and adventitia and thereby provides the basis for the assessment of the degree of coronary artery stenosis, extent of atherosclerosis burden (i.e. global and local disease burden), and plaque composition. All this represents key information to plan and perform percutaneous coronary intervention procedures in native coronary artery disease or graft lesions and to estimate the risk for future cardiovascular events.