What's it like to build your own airplane? Why are strong bones important? How did the tradition of a wedding cake begin? The Password series uses readings about real people, places, and events to help students develop reading skills and increase their active vocabulary. Each book's six theme-based units — including such universal topics as work, travel, and celebration — feature appealing passages, carefully chosen vocabulary, and a variety of exercises to engage and motivate readers. Units are followed by a four-part Wrap-Up section, which uses review and expansion exercises, puzzles, and dictionary skillbuilders to consolidate and enrich students' understanding of new words.