Schools in Colorado are trying to find effective ways to teach the health effects of marijuana use. "When it's legal for your parents to smoke it or grow it," says one educator, "that changes the conversation." David Zalubowski/AP hide caption

itoggle caption David Zalubowski/AP

The size of the brain of a chimpanzee (right) is considerably smaller than that of a human brain. Probably multiple stretches of DNA help determine that, geneticists say. Science Photo Library/Corbis hide caption

itoggle caption Science Photo Library/Corbis

Measles is highly contagious, and it produces fever and rash in susceptible people who become infected. Hazel Appleton/Health Protection Agency Centre/Science Source hide caption

itoggle caption Hazel Appleton/Health Protection Agency Centre/Science Source

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

itoggle caption iStockphoto

Eastman Chemical went a step beyond calling Tritan plastic BPA-free, setting off a legal challenge. Eastman hide caption

itoggle caption Eastman

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

itoggle caption Mark Harmel/Science Source

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. Howard Harris hide caption

itoggle caption Howard Harris