Who were the first animals on Earth? What differentiates a reptile from an amphibian? How do mammals give birth? What are bird wings made of? This boxset of six encyclopedias will answer these and more hows and whats for you. Learning is made simpler with well-labelled diagrams and an extensive glossary of difficult words. Bonus: the books in the boxset come loaded with Isn't It Amazing-- a section of fun facts to keep you glued for more.