Who's there? A radiologist studies digital X-rays in a viewing room at what is now called the Walter Reed National Military Medical Center in Bethesda, Md. Seth Rossman/U.S. Navy hide caption

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Scientists say that the best way to reduce a person's contact with the flame retardant chemicals in sofas and other furniture is to vacuum more. SINAN DONMEZ/iStockphoto.com hide caption

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At a Los Angeles media briefing in 2010, Mariah Bianchi describes how her own case of whooping cough caused the death of her newborn son. Reed Saxon/AP hide caption

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A young man places an oral swab into a solution to complete an HIV test during a free screening event in Washington, D.C. Brendan Smialowski/Getty Images hide caption

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Grapefruit can make for a tasty addition to breakfast. But it can also interfere with some medications. iStockphoto.com hide caption

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Pathologist Thomas Harvey took dozens of photos of Einstein's brain. This one shows that Einstein's prefrontal cortex (associated with higher cognition and memory) is unusually convoluted. On the right side of the brain there are four large ridges, where most people have only three. Brain(2012)/National Museum of Health and Medicine hide caption

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Stefano Amabili walks under the sun in Miami Beach, Florida, in May. The Center for Disease Control and Prevention has found that more people are using sunscreen and protecting themselves from the sun's rays. Joe Raedle/Getty Images hide caption

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Pathological nail biting may be a form of grooming on steroids, but it also makes the biter feel good, unlike fear-driven OCD. Andrea Kissack for KQED hide caption

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Nail Biting: Mental Disorder Or Just A Bad Habit?

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