Lake Ontario may be the smallest Great Lake, but its waters run deep.

Lake Huron has the longest shoreline of the Great Lakes. It is the second largest by surface area and the third largest by volume of water.

The largest Great Lake is superior in more ways than one.

Lake Erie, the fourth largest Great Lake, is also famous for a battle in the War of 1812 and for the Erie Canal.

The Serengeti is a vast ecosystem in east-central Africa.

Medical marijuana is legal in some states, but debate rages on about whether the health benefits outweigh the risks.

Lake Michigan is the only Great Lake located entirely in the United States.

Denali, formerly known as Mount McKinley, rises more than 20,000 feet above sea level.

The Cenozoic Era began about 65 million years ago and continues into the present.

The 650 muscles in the human body control movement and help to maintain posture, circulate blood and move substances throughout the body.

The human digestive system converts food into nutrients that the body needs.

Some experts say camel's milk may help fight a number of diseases, including diabetes, cancer, shingles and autism.

Thousands died and millions were left homeless in the most destructive storm to hit the United States.

Panic disorder is marked by sudden and repeated bouts of extreme fear that can last for several minutes or even longer. These episodes are referred to as panic attacks.

Post-traumatic stress disorder (PTSD) can occur after a person experiences a traumatic event, such military combat, a natural disaster, or a crisis such as 9/11.

The pulse rate measures the rate at which blood pressure increases throughout the body. There are several places on the body where you can find your pulse.

Memory involves encoding, storing, retaining and subsequently recalling information and past experiences.

Episodic memory is a person’s unique memory of a specific event; it will be different from someone else’s recollection of the same experience.

As the name implies, procedural memory stores information on how to perform certain procedures, such as walking, talking and riding a bike, without having to consciously think about them.

Implicit memory uses past experiences to remember things without thinking about them, like how to ride a bike or button a shirt.

Declarative memory, or explicit memory, consists of facts and events that can be explicitly stored and consciously recalled or "declared."

Semantic memory is the recollection of nuggets of information we have gathered from the time we are young.

Heart rate monitors provide immediate feedback on how hard you are working out so that you can make adjustments to get the greatest benefit from your exercise regimen.