Human biology

Have objects from space ever hit Earth?

What space objects can have millions of times more mass than our Sun, but they remain invisible?

What do bicycles, doorknobs, and screwdrivers have in common?

What do a doorstop, a butter knife, and the front of a boat have in common?

What do jar tops and water-bottle lids have in common?

What do flagpoles and some window blinds have in common?

What do hammers, wheelbarrows, and brooms have in common?

What do staircases, dump truck beds, and ramps have in common?

All kinds of animals have skin-even humans!

What animals have shells?

Some mammals have a little fur or hair, others have a lot!

See how birds use feathers for flight, warmth, camouflage, and much more.

Have you ever wondered how stars are born?

Uncover seven wonders of the four rocky planets.

The universe is full of space phenomena, such as dark matter, dark energy, and the beginning of the universe.

From earliest times, humans have wondered about the sky above them.

From earliest times, humans have looked to the sky in wonder, and their wonder and curiosity fueled science.

From earliest times, humans have wondered about the sky above them and have studied all visible objects.

From earliest times, humans have wondered about the sky above them.

Congratulations, insect parents-to-be!

A pot of water boils over a hot burner on the stove.

Light shines through your kitchen window.

Ice cubes clink in a glass.

Fireworks crackle and boom in the sky.

A light beach ball floats on the water.

Lightning streaks across the sky.

In North America, mosquito bites are usually only a nuisance.

An airplane soars through the sky.

A baseball player slides on the ground to tag a base.

A ball drops to the ground.

You push a swing.

A rock sinks in the water.

Every month a cycle happens in the sky.

Day follows night.

There is no gravity in space.

It takes seven years to digest swallowed gum.

This lively and informative book introduces beginning readers to the Sun, which is the center of our solar system and the system's largest object.

This lively and informative book introduces beginning readers to the planets, dwarf planets, asteroids, and comets that make up our solar system; the Sun as the center of the solar system; and more.

This lively and informative book introduces beginning readers to the Moon's orbit around Earth, phases of the Moon and eclipses, the Moon's effect on tides, and more.

This lively and informative book offers beginning readers a simple introduction to the Milky Way.

Have you ever seen a shooting star?

The body repairs and renews itself again and again - in cycles.

Welcome to the Australian Outback!

Welcome to the arctic tundra!

Welcome to an African Savanna!

Welcome to a South American rain forest!

Welcome to the desert!

Welcome to a North American estuary!

This book describes Venus, the second planet from the Sun.

This book describes the planet Saturn, the sixth planet from the sun and the second largest planet in the solar system, after Jupiter.