The "king of herbs" is considered by practitioners of Chinese medicine a remedy for almost any disease. It has been ingested one way or another for more than 5,000 years. Contemporary analysis shows that the roots contain a unique class of compounds called ginsenosides that are believed to strengthen the immune system and mitigate the effects of stress. There are about 15 ginseng species in Asia and two in North America. National Geographic sponsored two study trips, one by botanist Jun Wen and another by botanist Greg Plunkett, on expeditions to China to analyze the plant and its complex lineages. (Panax ginseng)