Light micrograph of a section through a lung where the cellular tissue has been removed, leaving only the collagen fibres that support the lung structures. This still allows us to see some of the structure of the alveoli (air sacs) and bronchioles of the lungs. The bronchioles carry inhaled air from the upper airway to the alveoli, the site of gaseous exchange, where oxygen enters the blood and carbon dioxide is removed. Magnification: x100 when printed at 15cm wide.