If you're trying to quit smoking, this could be the day you go cold turkey. The healthy lung (left) is generally pinkish and healthy, with a bit of damage from living in an urban area. The unhealthy lung (middle) comes from a smoker, and is riddled with dark tar from cigarettes.
What's even more worrisome than tar, according to Dr. Oz, is cancer. A cancerous lung (right) will have nodules of cancer cells that grow and spread, invading into everything around them.