The number of women buying, selling and sharing breast milk is growing rapidly. But it can be a risky purchase, scientists say, because a mom can't tell by looking at the milk whether it's safe and nutritious for her baby. iStockphoto hide caption

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Frito-Lay reformulated Flamin' Hot Cheetos, a perennial favorite among school kids, to meet new federal "Smart Snack" rules for schools. Meredith Rizzo/NPR hide caption

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Both James Eversull (left) and Pat Patchell were treated with experimental chemotherapy and radiation for leukemia as children in the 1960s. Together, they're now some of the country's oldest leukemia survivors.. Courtesy of James Eversull; Courtesy of Pat Patchell hide caption

itoggle caption Courtesy of James Eversull; Courtesy of Pat Patchell

Brazilian mothers participate in a demonstration in 2011 for the right to breastfeed in public, in Sao Paulo, Brazil. Eduardo Anizelli/STF/LatinContent/Getty Images hide caption

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Truvada can dramatically reduce the risk of HIV infection when taken as a preventative medicine — if taken every day. Studies are underway to determine if young people are likely to take the pill consistently. Justin Sullivan/Getty Images hide caption

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Having a narcissistic parent doesn't mean you're going to turn out that way, too. GraphicaArtis/Corbis hide caption

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Kristen Caminiti cuddles her son Connor while doctors stitch her up following a C-section. Courtesy of Kristen DeBoy Caminiti hide caption

itoggle caption Courtesy of Kristen DeBoy Caminiti

Uzuri Pease-Greene, right, leads a walk through the public housing complex in the Potrero Hill neighborhood of San Francisco where her family lives. She is working to have the old buildings replaced. Talia Herman for NPR hide caption

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Hanna Barczyk for NPR

Most parents have a favorite child, psychologists say, even if they try to be fair. Hero Images Inc./Corbis hide caption

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People who practice free-range parenting say it makes kids more independent, but others see it as neglect. State and local laws don't specify what children are allowed to do on their own. iStockphoto hide caption

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A health worker with Doctors Without Borders carries a child suspected of having Ebola at the treatment center in Paynesville, Liberia, last October. Ebola is especially deadly for young children and babies. About 4 in 5 infected died. John Moore/Getty Images hide caption

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The ParaGuard IUD, which releases copper into the uterine cavity, can last up to 10 years. In clinical studies, the pregnancy rate among women using the device was less than 1 pregnancy per 100 women annually. Mark Harmel/Science Source hide caption

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Mary Harris was relieved when Stella was born with a mop of thick black hair, as if she had been protected from the chemo somehow. Courtesy of Howard Harris hide caption

itoggle caption Courtesy of Howard Harris