LOBSTERS Can you grow a new body when you get too big for your old one? Of course not. But lobsters can. They keep growing their whole life. As a lobster grows, it often molts. This means that it grows a new shell and casts off its old one. It even regrows any legs or...

GREAT WALL OF CHINA Imagine a huge wall stretching for thousands of miles across the land. The wall winds through hills, climbs mountains, and crosses deserts. If you visit China you can see a wall like this. The Great Wall of China, as it is known, is the longest...

PAUL REVERE On April 18, 1775, in the dark of night, Paul Revere awoke to pounding on his door. Friends brought news: British troops were on the move! Revere pulled on his clothes and jumped on a borrowed horse. Along with two other horsemen, he galloped from his home...

People exercise to keep healthy. They exercise to lose weight or to stay fit. They exercise to make their muscles bigger and stronger. Maybe you play soccer or some other sport for exercise. Getting exercise can be fun and can make you feel good.
Exercise is a big part of staying physically fit. People who are physically fit are alert and full of energy. Exercise can also help people handle stress. Exercise is especially good for children, teens, and older persons.

Imagine how frightened prehistoric people must have been when they saw a black disk covering up the Sun. This darkening of the Sun in the middle of the day is called an eclipse. The Moon can go dark in a similar way at night. Eclipses are caused by shadows.

What is the difference between an alligator and a crocodile? That’s kind of a trick question. “Crocodile” is a common name for an order, or large group, of animals called crocodilians. Alligators, caimans, and gavials are all crocodilians—but so are crocodiles.

When you play with friends, who gets to choose the game? Do you all decide together? Do each of you play a part in the decision? If so, you and your friends are a democracy.
Usually, when we speak of a democracy, we mean a country. In a democratic country, the people choose how they will be governed. Most of the time, they do this by electing leaders who run the government.

They called him “the man with a million stories.” People flocked to Marco Polo’s home to hear him tell exciting tales about his travels in distant lands.
Marco Polo won fame for his journeys across Asia. He wrote a book about his travels that became one of the most famous travel guides in history.

Ice cream is a frozen treat that comes in hundreds of flavors. What’s your favorite flavor? Is it vanilla? That’s the most popular flavor by far. Chocolate ranks second in popularity.
Ice cream is especially popular in the United States. In fact, Americans eat more ice cream than people in any other country.

You know what kind of weather to expect at each time of year, at least for the place where you live. That's because you're familiar with the climate—the typical range of weather for a region. Did you know that Earth's climate hasn't always stayed the same? Every once...