If you're interested in buying Viagra, Pfizer, the drug's maker, will now sell it to you from its official website. William Vazquez/AP hide caption

itoggle caption William Vazquez/AP

A PET scan of the brain of a person with Alzheimer's disease. U.S. National Institute on Aging/via Wikimedia Commons hide caption

itoggle caption U.S. National Institute on Aging/via Wikimedia Commons