Every four years something funny happens with our calendars -- we add a day! Why do we do this? Discover the science behind leap year.

Meet the red wolf, an endangered species of animal that was once very common, but in the past 50 year nearly became extinct!

Did you know that some caribou travel 3,000 miles in a year? This fun worksheet is jam-packed with fun facts about the caribou!

Learn facts about Venus, the planet that shines the brightest in our night sky! Then practice your knowledge of the solar system with bonus trivia at the end.

Learn about the grizzly bears that live in Yellowstone National Park.

Discover the science behind an ages-old 4th of July tradition with this firework diagram.

Learn about the Uinta ground squirrels of Yellowstone National Park.

It's easy being green when you have our Earth Day game for a guide. Just print out this Earth Day game and get ready to score one for the planet.

Learn about the science behind one of nature's most awesome spectacles: monsoons.

This science worksheet tells all about James Watt, the man that powered the Industrial Revolution.

What is geothermal energy? Find out how we use parts of the Earth to provide us with renewable energy!

Get swept up in this comprehensive worksheet about the awesome power of dust storms.

Nature is all around us! But how much does your child know about our natural world? Test her knowledge with some nature fun-facts trivia.

Learn all about the science of the movies and the basic concepts behind how they work.

Dive into the deep, vast world of ocean science with this introductory sheet on the world's different oceans.

Looking for a fourth grade worksheet to help your kid with science? This printable will test his knowledge of the water cycle.

Launch into learning with this worksheet on Gemini 4, one of the original missions in the early days of the U.S.'s space program.

Learners will discover a simple overview of the human muscle system in this introductory worksheet.

Use your powers of prediction to project the future movement of playground objects!