University of Miami pediatrician Judith L. Schaechter gives an HPV vaccination to a 13-year-old girl last week in Miami. Joe Raedle/Getty Images hide caption

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Seeds from Golden Rain acacias like these in Wales provide the active ingredient for a pill to help people stop smoking. Tom Patterson/Flickr hide caption

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True North Health Center in Falmouth, Maine, accepts "time dollars," in addition to real dollars. Patients perform services in the community, like raking leaves, to earn the currency, and they can spend it for care at True North. iStockphoto.com hide caption

itoggle caption iStockphoto.com