Angiography is a medical imaging technique used to visualize the inside of blood vessels and organs. It involves the injection of a contrast dye into the bloodstream, which makes the blood vessels visible on X-ray images. This procedure helps doctors diagnose conditions such as blockages, aneurysms, and other vascular diseases. The most common type of angiography is coronary angiography, which focuses on the heart's blood vessels. Other types include cerebral angiography for the brain and pulmonary angiography for the lungs. Angiography is often performed in a hospital setting and can guide treatment decisions.