A healthy lung, an unhealthy lung and a cancerous lung

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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.