Tips & Special Features:
At the top of the 21st Century Explorer screen are to "Level" buttons ("Level 1" and "Level 2").
"Level 1" is the easiest, while "Level 2" is for more advanced readers.
Other tips:
Instead of searching, you can browse topics such as Arts, Science, and Social Studies in 21st Century Explorer.
Also check out the "Features" section on their page for Biographies, Timelines, a World Atlas, and more.
If you need more information that what is provided in 21st Century Explorer,
consider one or more of the "related resources" link to the right of this page.