The heart, lungs and about 60,000 miles of blood vessels work together to keep blood pumping through our bodies.

Humans wouldn't get very far without bones — literally.

Social anxiety disorder isn't just being shy.

Sometimes, at sunset, the sun appears to suddenly and briefly change color. Blink, and you'll miss it.

People who experience generalized anxiety disorder (GAD) exhibit excessive anxiety and worry about multiple events or activities most days of the week.

Skin is the body's largest organ and is the first line of defense against harm.

The job of the immune system is to protect against disease.

This may be the most important system in the body. Without the ability to reproduce, a species dies.

The urinary system — also known as the renal system — produces, stores and eliminates urine, the fluid waste excreted by the kidneys

The lymphatic system helps rid the body of toxins. Diseases of this system include lymphadenopathy, lymphoma and other disorders.

The endocrine system is a collection of glands that secrete hormones.

The network of nerves is the body's electrical wiring.

Chinese culture reflects the customs and traditions of one of the largest countries in the world, with 1.34 billion people.

The Andean peak is also the highest in the Western and Southern hemispheres.

Italian culture, steeped in the arts, architecture, music and food, has flourished for centuries. Here is a brief overview of Italian customs and traditions.

The history of computers starts with industrial and governmental needs, which led to huge machines and eventually the Internet, mobile phones and gaming systems.

Called different names in different parts of the world, these storms are powerful and deadly.

The Pleistocene Epoch began about 2.6 million years ago and lasted until about 11,700 years ago.

The customs and traditions of France, center of fashion, art and architecture.

India is one of the world's oldest and most diverse cultures. Here is an overview of Indian customs and traditions.

The culture of Mexico varies widely throughout the country, but traditions are highly valued.

Nearly every region of the world has influenced the customs and traditions of the United States.

Culture is the characteristics of a particular group of people, defined by everything from language, religion, cuisine, social habits, music and arts.