This is a resin cast of blood vessels from some corrective tissue, viewed with a scanning electron microscope at a magnification of 130 times. The cast was made by injecting resin into the vessels and removing the surrounding tissues once hardened. The smallest vessels, capillaries, branch off the main vessels, forming networks that carry blood into the tissues. Oxygen and nutrients pass through their permeable walls and into the tissues. Waste products, including carbon dioxide, pass back to be carried away.