Volunteers who take part in clinical trials usually start by answering a host of questions about their health and habits. Those who qualify to take part may be asked to take experimental drugs, experimental therapies (such as acupuncture to treat headaches), new food supplements or exercise regimens.

Scientists moved some northern quolls, such as these, to a predator-free island. After 13 generations, however, the quolls lost their protective fear of predators.

The difference between the numbers of men and women in many STEM fields has shrunk. But it could still take decades or even centuries in some disciplines to close the gender gap.

Teens who downed restaurant, cafeteria or carryout food in the past day had far higher levels of certain potentially harmful chemicals in their bodies than did teens who ate only home-cooked meals.