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

What has two legs and carries its baby in a pouch? Fill in this crossword puzzle and learn some fun facts about two-legged creatures!

Dive into the electrifying concept of electrical energy in this colorful worksheet!

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!

Practice classifying different animals in this engaging life science worksheet, created for second and third graders!

Students practice classifying items as liquids or solids for a lesson on the states of matter in this fourth grade physical science worksheet.

Who will win the marble race in this two-page physical science worksheet?

Use this cool 2-page worksheet to make your own big dipper clock!

Match forms of energy to common examples in this third- and fourth-grade science worksheet!

Explore the strength of magnetic forces with this worksheet for third and fourth graders!

In this worksheet, children practice identifying animals of North America by their tracks.

Learn to identify and name the parts of a seed in this two-page science worksheet and quiz!

Fly high with The Wright Brothers, two siblings who soared to the forefront of history with their design for the first modern airplane.

Cave formations come in all kinds of shapes and sizes; get the scoop on common cave formations with this two page printout with a maze and vocabulary.

Uncover secrets of the past with this third-grade worksheet about fossils!

These are the largest tortoises in the world, yet they are only two inches long when they hatch! That's one of the facts you can learn from this worksheet.

Think toads and frogs are the same? Think again! Check out this breakdown of the differences between the two, complete with a quiz to check your new knowledge.

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.