Lots of kids get scared when their bedroom lights go out at night. When an entire city goes dark, many more people start to worry.

Government and utility officials are still scrambling to explain a blackout that hit much of the northeastern United States in late summer. From Detroit to New York, lights went out. Refrigerators, traffic signals, elevators, and subway trains stopped working. Computers went dead.

  Without electricity, people had trouble getting to work, shopping for groceries, and communicating with each other. Normal life pretty much shut down for a few days.

  Electricity also plays a crucial role within the human body. A lightning bolt or shock can disrupt or shut down that flow, causing disability or death.

  "Electricity is life," says David Rhees, executive director of the Bakken Library and Museum in Minneapolis. The Bakken museum is dedicated entirely to the history and applications of electricity and magnetism in biology and medicine.

   The museum has a lot to keep up with. As scientists learn more about the electrical signals that whiz through our bodies and the electrical pulses that tell our hearts to beat, they are finding new ways to use electricity to save lives.

  Research on the nervous systems of animals and people are helping scientists design machines that help diagnose and treat brain conditions and other problems. New drugs are being developed to regulate the body's electrical pulses when things go wrong in response to injury or disease.