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.

The vagus nerve runs from the base of the brain down the spinal cord, and reaches out to touch most of your organs along the way. The yellow line in this picture is the top of the vagus nerve, here attached to a small electronic stimulator. That device can be used to treat seizures or depression.

Tall structures, such as skyscrapers, radio towers and wind turbines, may create conditions that greatly up the chance of cloud-to-ground lightning during windy snowstorms.