Blood vessel stents. Variety of experimental vascular stents, with a pin (left) for scale. Stents are wire tubes that are used to treat stenosis (narrowing) of blood vessels. A balloon catheter (not seen) that passes through the middle of the stent is used to guide it into place in the artery. Once in place the balloon is inflated to expand the stent and open the blood vessel. The balloon is then deflated and removed, leaving the stent behind.