Did you know that about 200 billion apps are downloaded worldwide each year? Apps have been developed to help first responders, control smart-enabled devices, and entertain and delight. Learn more about this diverse technology in Apps, part of the 21st Century Technology series. This series takes young learners through the science behind some of the world's most exciting technological innovations. 21st Century Technology is a series of AV2 media enhanced books. Each title in the series features easy-to-read text, stunning visuals, and a challenging educational activity. A unique book code printed on page 2 unlocks multimedia content. These books come alive with video, audio, weblinks, slide shows, activities, hands-on experiments, and much more. Follow these steps to access your AV2 book. Step 1 Find the code on page 2 of this book. Step 2 Enter the code at www.av2books.com. Step 3 Explore the AV2 media enhanced book. Book jacket.