Light micrograph of the wall of an aorta with an aneurysm, or an abnormal dilation of its wall. Aortic aneurysms can be life-threatening if they rupture or impair blood flow to essential organs. Histologically, the elastic fibres (black, wavy lines) have been disrupted and separated by matrix material (pink area), a phenomenon known as medial degeneration. Magnification: 100x when printed at 10 cm.