This 3D medical animation shows lungs expanding and contracting with each breath. Camera zooms into lungs to show airway branches and then continues to zoom into small branch at of lung to see air sac, with the internal structure of a bronchiole airway tube, showing air molecules rushing in and out as the person inhales O2 in and CO2 out. The camera then zooms into a capillary, allowing the viewer to see oxygen molecules leave the area sac and enter the blood flow oxygenating the blue blood cells and turning them instantly red.